Capl 






ADVERTISEMENTS. 



NO MORE SOUR BREAD. 



GOLD AND SILVER MEDALS 

AND THE 

JDTFTiOHsKJk. OIF lEIOZLSTOTTIR. 





ONCE TRIED, ALWAYS USED. 
THE ENCORE JS THE CHEAPEST 
BECAUSE THE STRONGEST FRENCH YEAST OUT 



The great 

strength, 

purity, 

fine colour, 

sureetflavour, 

and 

remarkable 

keeping 

qualities 



R.O.BISCHOFS 

ENCORE YEAST 

i 30.BR00KE SlWWON,£.C. 



make the 

ENCORE 

essentiafly 

the Yeast for 

high class 

Bread, Buns, 

and 

all small 

Goods. 



"Park Roads, Liverpool, March 2nd, 1885. 
" Sir, — I have much pleasure in adding my testimony to the superior quality of 
your Encore Yeast, HAVING TRIED IT AGAINST A GREAT MANY OTHER 
AND DEARER YEASTS, HAVE GIVEN IT THE PREFERENCE. Having 
now been using it for about nine months, am pleased to say that it has given satis- 
faction to my customers. 

" HENRY LEECH, Chairman Master Bakers' Association." 



W& ENCORE YEAST ALMANACK. "d 

Post free on application. Nobody should remain without it. Highly interesting 
information about the manufacture of Yeast, illustrations of Yeast cells under the 
Microscope, views of the Factories and their Machinery, most useful recipes and 
directions for use for Bread, Buns, &c. Testimonials, &c. 

DRIED WHITE OF EGG, 

A SPECIALITY. 

Simply the "White of the best and freshest Eggs care- 
fully dried. Keeps any length of time, avoids all trouble 
of stale Eggs, and recommends itself by its handiness. 
and economy where there is no immediate use for the 
yolks, and in fact, for all purposes where the fresh 
white is used. 

A Boon to the Cook, Confectioner, & Biscuit Baker, 

jerTry it— Ever ready. Samples free. 




Regd. Trade Mark. 



R. O. BISCHOF, ENCORE YEAST IMPORTER, 

30, Brooke Street, Holborn, LONDON, E.C., and at BRIGHTON and BRIXTON. 

1 



if ADVERTISEMENTS. 



MR. WILLIAM JAGO, 

HAVING BEEN PROFESSIONALLY TRAINED BOTH AS A 

PRACTICAL ENGIN EER and CHEMIST, 

OFFERS HIS SERVICES AS A 

CONSULTING BAKERS' ENGINEER, 

AND 

ADYISES ON ALL QUESTIONS CONNECTED WITH THE 

ALTERATION OF EXISTING, OR THE 

BUILDING OF NEW BAKEHOUSES 

AND THE 

ADOPTION AND SELECTION of MACHINES and OVENS; 



Complete Plans and Estimates of cost of Alterations, or Erection of 
New Bakeries, prepared. 



To Inventors of Baking Machinery and Specialities. 4 ^! 

Mr Jago is prepared to advise on the subject of patenting inven- 
tions in this special department, and to act as Patent Agent, procuring; 
both provisional and complete Patents at the usual fees. 

Having had special experience of Bakeries and Baking Machinery, 
and not being interested in the sale of any particular Machine or 
Oven, Mr. Jago hopes that his services as a purely Consulting Bakers' 
Engineer, as distinct from the manufacturer and vendor of baking. 

machinery, 

Will supply a long felt want. 



For Ter?ns and Full Particulars, Address— 

138, Springfield Road, Brighton. 



ADVERTISEMENTS. 111. 



ON SUBJECTS CONNECTED WITH THE 

CHEMISTRY OF WHEAT, FLOUR, & BREAD. 



Inorganic Chemistry, Theoretical and Practical, by 

William Jago, F.C.S., F.I.C. Longmans & Co. Price, 
Two Shillings. 

Cantor Lectures on The Chemistry of Breadmaking, 

by C. Graham, D.Sc, Society of Arts. Price, One Shilling. 

Studies on Fermentation, by L. Pasteur. Macmillan & 
Co. Price, Twenty-one Shillings. 

Fermentation, by P. Schutzenberger. Kegan, Paul & Co, 
Price, Five Shillings. 

Bacteria and Yeast Fungi, by W. B. Grove, B.A. Chatto 
& Windus. Price, Three Shillings and Sixpence. 

Practical Bacteriology, by E. M. Crookshank, M.B., F.E.M.S. 

H. K. Lewis. Price, Fourteen Shillings. 

Analysis and Adulteration of Foods, by James Bell, 
Ph. D., Part II. Chapman & Hall. Price, Four Shillings 
and Sixpence. 

Foods, Composition and Analysis, by A. W. Blyth, 
M.E.C.S., F.C.S. Charles Griffin & Co. Price, Sixteen 
Shillings. 

Commercial Organic Analysis, by Alfred H. Allen, 
F.I.C, F.C.S. J. & A. Churchill. Price, Fifteen Shillings. 

Flour Testing Table, by W. A. Thoms, F.E.M.S. W. A. 

Thorns, Alyth, KB. Price, One Shilling and Sixpence. 



IV. ADVERTISEMENTS. 



SCIENCE SCHOOLS, BRIGHTON. 



& $f>edial Ciouf^e of ¥edl|i|idkl IqjJtfudtion 

MILLING & BAKING SCIENCE 



IS GIVEN BY 



MR. WILblAM JAGO, F.6.S., F.I.C., 

Analytical and Consulting Chemist, Author of i< A Confidential Report on Wheat 
and Flour Supply" &c. 



The course of Study includes the Chemistry and Microscopy of 
Wheat, Flour, Yeast, &c, Mathematics, Mechanical Draw- 
ing, Principles of Mechanics, The Steam Engine, Heat and 
Electricity ; providing such a grounding in Science as will enable 
the Student on entering on his Practical Course as a Miller or Baker 
to appreciate, and to be guided by the Scientific Principles under- 
lying his work. 

FEES. 

Per Month Six Guineas. 

Per Term of about Three Months Fifteen Guineas. 

Per Year of Three Terms Forty Guineas. 

RESIDENT PUPILS 

Are received by Mr. Jago, at his private residence, at a charge of 
Twenty Guineas per Term. 

All Fees must be faid in Advance. 

The Terms commence on or about the 21st September, 7th Janu- 
ary, and 15th April, of each year; but Students may join the School 
at any time, in which case the fees are reckoned from the date of 
joining. 

The Course of Chemical training in the Laboratory, and general 
instruction, is also recommended for those who purpose to become 
Brewers, Farmers, &c. In every case the course of study is arranged 
to suit the special requirements of each individual Student. 

The great value of such a course of scientific study being universally 
admitted, Mr. Jago suggests that it conveniently follows, or may even 
with advantage take the place of, the last two or three terms of 
ordinary schooling. 

Mr. Jago will be pleased to forward a Prospectus of the School 
and to give advice and every information, on application either per 
sonally or by letter. 



ADVERTISEMENTS. 



A 

CONFIDENTIAL REPORT 

ON THE 

WHEAT & FLOUR SUPPLY 



THE UNITED KINGDOM, 

FOR THE PRIVATE USE OF 

MILLERS, BAKERS, CORN, AND FLOUR MERCHANTS. 



WILLIAM JAGO, F.C.S., F.I.C, 

Jlnalgtiral anb Consulting (Ehemist. 



This Publication is issued for the purpose of giving Subscribers 
information on the results of Commercial Tests on Wheats, 
Flours, and Yeasts. Samples are collected from various sources 
and specially analysed for this Eeport. 

Every Subscriber has the right each year to forward two 
samples, which are tested gratis ; the results and description of 
the samples are published in the Eeport. 

Other analytic investigations, on subjects of interest to Millers 
and Bakers, are from time to time made and the results inserted. 

On receipt of Cheque or Postal Order for Ten Shillings, the 
Eeport for One Year will be forwarded, post free, as issued, to 
any address in the Postal Union. 

From Four to Six Numbers are issued annually. Specimen 
Copy forwarded on application. 



ADDRESS- 



138, Springfield Road, BRIGHTON. 



ADVERTISEMENTS. 



COMMERCIAL TESTING AND ANALYSIS 

OF 

Wheats, Flours, and Yeasts, 



Analytical Work of the above, or other description, Is performed 



BY 



WILLI/cM JJkQO, f.e.S., J.I.C., 

^tnatgtiral an& Consulting Chemist. 



In case of the occurrence of SOUR BREAD, or other irregu- 
larity of Production, consult Mr. JAGO, for advice as to its 
CUEE and PREVENTION. 

MILLERS and BAKERS tendering for Contracts to supply 
Elour and Bread should have DUPLICATE SAMPLES ANA- 
LYSED AND REPORTED ON, and THUS PROTECT 
THEMSELVES IN CASE OF AFTER DISPUTE. 

Samples of Flour, accompanying Tenders for supply of public 
bodies, examined and their comparative merits reported on. 



Analytical and Chemical Investigations conducted. 



Terms and Full Particulars on Application. 

Special Estimates given for the making of large numbers of 
COMMERCIAL TESTS and ANALYSES. 



ADDRESS— 

138, Springfield Road, BRIGHTON. 






ADVERTISEMENTS. 



THE MILLERS' GAZETTE 

CORN TRADE JOURNAL 

IS THE WEEKLY ORGAN OF MILLERS. 



// is full of fresh and interesting articles 
on all topics pertaining to the Milling 
and Grain Trades, 



The earliest information and descriptive 
articles of New Machinery for Millers 
are given. 

IT IS PUBLISHED IN CONNECTION WITH 

J. E. BEERBOHM'S 
Evening Corn Trade List, 

Which it accompanies as a Supplement every Monday. 



Subscription to the Millers' Gazette, 12/6 p, annum, 

Subscription to the Evening Corn Trade List (daily), 
including the Millers' Gazette, £5 15/- p. annum, 
post free, 

Published by J. E. BEERBOHM, 
At 28, Bishopsgate St Within, London, E.G. 



ADVERTISEMENTS. 



J. HARRISON CARTER 
§xwtd< mA $tmtd 

The First Patented Auto- 
matic Roller Plant in the 
world, which finished off all 
the products in one continu- 
ous operation. 



The CARTER System was also the 
first in which no Continental of Ameri- 
can expert took a leading part. 



82, Mark Lane, LONDON. 

1, RUE SARTINE, PARIS. 



ADVERTISEMENTS. IX. 



THE CARTER 



ROLLER SYSTEM. 



This System is at work in the Mills of 
six of the present Members of the Council 
of the British and Irish National 
Association of Millers \ and lines of the 
Carter Rollers Mills are also at work in 
the Mills of four out of the six Presidents 
of the Association. 



J. HARRISON CARTER, 

82, Mark Lane, LONDON 

1, RUE SARTINE, PARIS. 



ADVERTISEMENTS. 




CARTER'S MACHINES 

Are entirely of Home Manufacture, and exhibit 
the characteristics of British Design and 
Workmanship, viz : — 



J. HARRISON CARTER, 
82, Mark Lane, London; 1, Rue Sartine, Pahs. 



INDEX TO ADVERTISEMENTS. 



American Miller, The, 

Baker & Sons, Baking Engineers, . 
Bischof, R. O., "Encore" Yeast, . 
Boehme & Meyer, " Hansa" Yeast, 
Book List, ....... 

British and Foreign Confectioner, The, . 

Carter, J. Harrison, Milling Engineer, . 

Chatterton, J. H., Fire Insurance, . 

Confidential Report on Wheat and Flour Supply, 

Corcoran, Bryan, Milling Engineer, 

Duncan Watson & Co., " Olivoline," 

Germ Milling Co., ..... 

Graham, W., & Sons, Oven Fittings, 
J ago, W., Consulting Chemist and Engineer, . 
Mason, W. F., Baking Engineer, . 
Mawson & Swan, " Pure Rye " Yeast, 

Miller, The, 

Miller's Gazette, The, 

North-Western Miller, The, .... 

Orme & Co., Chemical Apparatus, 

Porter, L. C, Milling Co., . 

Simon, H., Milling Engineer, Special Position between pp. 304-5, 



Swift & Son, Microscopes, ..... 
Technical Instruction in Milling and Baking Science, 

Thompson Bros., Gas Ovens, 

Vicars, T. & T. , Ovens and Biscuit Machinery, 
Watson, J. & Co., " Levure Doree" Yeast, . 
Wilkins, D., " En Avant " Yeast, 



vm 



PAGE. 

xxxvi. 

xx., xxi. 

i. 

xxxii. 

iii. 

xvii. 

ix., x. 

xv. 

v. 

xvi. 

xvi. 

xvi. 

xxiii. 

xxxii. 

xxix. 

xviii. 

xxxiv., xxxv. 

vii. 

xxxiii. 

XXV. 

xxxi. 



xxvn 



Xlll., XIV., xxxvu 



XXIV. 

iv. 



Cspt Henry G, Sharpy a &, (/, S, 4, 



THE CHEMISTRY 



WHEAT, FLOUR, AND BREAD. 



LONDON PUBLISHERS: 

Messrs. SIMPKIN, MARSHALL, HAMILTON, KENT & Co., 
Limited. 




CHEMIST 



OF 



WHEAT, FLOUR, AND BREAD 



AND 



TECHNOLOGY OF BREADMAKING. 



WILLIAM J AGO, F.C.S., F.I.C., 

ANALYTICAL AND CONSULTING CHEMIST, 
HEADMASTER, SCIENCE SCHOOLS, BRIGHTON. 

Author of " A Confidential Report on Wheat and Flour Supply" 
" Inorganic Chemistry \ Iheoretical and Practical" &c. 



BRIGHTON : 
WILLIAM JAGO, 

138, Springfield Road. 



1886. 



COPYRIGHT.] 



[all rights reserved* 



LESLIE, PRINTER, PERTH. 



7~3 a/yef 

• J} 



WP 



'•'■■■> 



Trans er 
6 6 

JUL 11 1942 

Accessions D vision 
ThaLBRARY of CONGRESS 



:-'? 



?$z 



u 



PREFACE. 



Having for some time taken particular interest in the study of the 
Chemistry of Wheat, Flour, and Bread, in 1883, I received an in- 
vitation from Mr. J. H. Chatterton, Secretary to the " National 
Association of British and Irish Millers," to read a paper on that 
subject at the Annual Meeting of the Association. That paper was 
received both by the audience and the various trade journals, represent- 
ing millers and bakers, in the kindliest possible fashion. A*s an 
immediate result, the Editor of the Millers' Gazette requested me to con- 
tribute a series of articles on the subject to that journal. The articles, 
to the number of sixty-four, duly appeared ; and on the conclusion of 
the series, the Editor, and other gentlemen interested in milling and 
baking, strongly urged me to republish them in book form. The present 
work now offered to the public is the result of my having followed their 
advice. 

My first idea was to reprint the articles almost exactly as they 
originally appeared ; but having commenced the task of re-modelling 
them I found the work growing on my hands until something like three- 
quarters of the matter of the book was entirely re-written. Hence a 
task which at its commencement I had hoped to have completed in a 
month has extended over a year. 

An inspection of the book will sufficiently show the nature of its 
contents : some few words of explanation of its objects are due to the 
reader. One of my aims has been to provide a text-book for such 
students as are anxious to make themselves acquainted with those 
departments of Chemistry and other allied sciences which have a more 
or less direct bearing on Milling and Baking. The earlier part of the 
work is devoted to an exposition of general principles, after which their 
application to practical work is described. I hope that in this capacity 
the book may be found of service by those who are preparing for the 
Technological Examinations of the City and Guilds of London Institute 
in Milling and Breadmaking. It has for some time formed the basis 
of the course of study through which my own milling and baking 
students have worked. Breadmaking is essentially a chemical opera- 
tion ; but in order to make my treatment of its Technology fairly 
complete I have introduced a chapter descriptive of modern Baking 
Machinery and Appliances. I have not attempted the same for Milling, 
because Machinery there plays so much more important a part that to 
have done so would altogether have altered the character of the present 



Preface. 



book : further, the subject has been already dealt with in previously 
written works. 

But in addition to the student, there is also the practical and busy 
man, who finds himself without the time and opportunity necessary for 
studying the subject from its foundation, but who nevertheless wishes 
to know the conclusions that may be drawn from scientific research, and 
their actual bearing on milling and baking operations. I have en- 
deavoured to so treat the subject as to place these conclusions in such a 
form as to be readily grasped by the general reader, who may wish to 
give them a practical application. 

As from time to time scientific articles are quoted in the trade 
journals, which frequently contain chemical terms and references that 
are necessarily unfamiliar to those who have not had a chemical training, 
I have explained in appropriate parts of this book such of these terms 
as have come under my notice. In order to facilitate reference, the 
index is made somewhat more comprehensive than is usual. 

In chapter XI., an account is given of some experiments I have 
recently made on yeast and problems connected with panary fermenta- 
tion. As some of these have been suggested by discussions that have 
appeared in the baking and milling organs, it is hoped they may throw 
light on points at present in dispute. 

I should like to direct the attention of both millers and bakers to 
the mode of Flour Testing by means of the instrument called the 
Viscometer, described in chapters XYI. and XX. They will notice 
that in various parts of the work results obtained by means of this 
apparatus are quoted : a study of these results will best indicate the 
kind of information it yields. It seems to me capable of affording very 
considerable help to producers and users of flour in accurately investi- 
gating and determining many of its properties. I have found in my 
own case that 1 have been able by its use to test and compare flours, 
not only at the same, but at different times, with a degree of precision 
and certainty I could not otherwise have hoped to attain. 

Although primarily written for Millers and Bakers, information is 
supplied which it is believed will prove useful to Yeast Brewers and 
Merchants, Engineers, Farmers, and others, who have a more or less 
•direct connection with the milling and baking industries. 

I also venture to hope that the work may be found of service to 
Chemists, as affording some slight contributions to the sum total of 
knowledge of Chemical Science. 

One of the pleasures of writing a preface to a work such as this is 
the opportunity it presents of expressing one's thanks for assistance 
rendered during its preparation. My thanks are due to Mr. Beerbohm, 
the proprietor, and Mr. Rush, the editor, of the Millers' Gazette. The 
production of this book is in large part due to the liberal encourage- 
ment and support I obtained from these gentlemen at the time my 
original articles in the Millers' Gazette were appearing. I have pleasure 
also in tendering my thanks to the proprietors and editors of the Miller 
and British and Foreign Confectioner, who have most readily and 
willingly given me any assistance in their power. Turning next to 
private gentlemen, I am deeply indebted to Mr. W. A. Thorns, F.R.M.S., 



Preface. 



of Alyth, N.B., for much advice and assistance. Readers of the 
work will see to what a great extent he has afforded me his valuable 
help. I also thank my assistants, and milling and baking students at 
the Science Schools, inasmuch as during the past three years they have 
at all times, " in season and out of season," cheerfully and readily helped 
me in the analytic work that has been necessary in order to obtain the 
results given in the present treatise. I append a list of the various 
scientific works and authorities I have consulted while preparing this 
book. It goes without saying that in writing the matter contained in 
its pages, I am greatly indebted to the various standard works on the 
subject. Many of these are books that ought to be in the possession of 
milling and baking students ; I have therefore given particulars of 
these, together with the names of publishers, and the prices, in one of 
the advertising pages in the front of the book. 

WORKS CONSULTED : 

Files of the Millers' Gazette, Miller, and British and Foreign Confectioner. 

Journal of the Chemical Society. 

Comptes Rendus. 

Cantor Lectures on The Chemistry of Breadmaking ; Graham. 

Studies on Fermentation ; Pasteur. 

Fermentation ; Schutzenberger. 

Bacteria and Yeast Fungi ; Grove. 

Technology of Bacteria Investigation ; Dolley. 

Manual of Brewing ; Hooper. 

Dictionary of Chemistry ; "Watts. 

Elements of Chemistry ; Miller. 

Commercial Organic Analysis ; Allen. 

Volumetric Analysis ; Sutton. 

Analysis and Adulteration of Foods ; Bell. 

Foods, Composition and Analysis ; Blyth. 

Composition of American Wheat and Corn ; Clifford Richardson. 

Bread Analysis ; "Wanklyn. 

Healthy Manufacture of Bread ; Richardson. 

Materia Medica, Pereira, &c. 

In dealing with so large a subject, I am conscious that I cannot' hope 
to have altogether escaped errors, both in the analytic work and the 
judgment based thereon. So far as possible I have carefully checked 
the former, and where I have thought any result uncertain, have indi- 
cated the same. In matters of judgment, I have impartially stated the 
opinions that the evidence in my possession has led me to form. In the 
natural order of things, such opinions cannot be expected to be final : 
where further evidence leads me to modify any of the views I have here 
recorded, I shall not hesitate to express my change of opinion. 

In conclusion, the generosity which has been exhibited toward my 
past contributions to milling and baking science gives me confidence 
that millers and bakers will also extend to the present work their 
favourable consideration. 

WILLIAM J AGO. 

Science Schools, 

Brighton, June, 1886. 



TABLE OF CONTENTS. 



CHAPTER I. page. 

Introductory. I 

General Scope of Work — Definition of Chemistry — Study of Chemistry necessary 
— Important Preliminary Statements and Definitions — List of Elements — 
Metals and Metalloids — Symbols and Formulae — Further uses of Symbols and 
Formulae : law of Chemical Combination by "Weight— Constitutional Formula) 
— Chemical Equations — Atoms and Molecules— Measures of Weight and 
Volume— The Metric System — English Weights and Measures — Heat 
Measurements — Temperature — The Thermometer — Thermometric Scales — 
Quantity of Heat — Expansion and Contraction of Gases — Avogadro's Law — 
Absolute Weight of Hydrogen — Laws of Chemical Combination by Volume — 
Acids, Bases, and Salts — Compound Radicals — Quantivalence or Atomicity — 
Basicity of Acids — Chemical Calculations — Percentage Composition from 
Formula — Formula from Percentage Composition — Calculations of Quantities 
— Gaseous Diffusion — Osmose and Dialysis — Crystalloids and Colloids. 

CHAPTER II. 

Description of the Principal Chemical Elements and their Inorganic 

Compounds. 21 

Description of Elements and Compounds — Hydrogen — Oxygen — Ozone — Water 
— Solvent Power of Water — Chlorine — Hydrochloric Acid — Chlorides- 
Bleaching Powder, or Chloride of Lime — Carbon — Carbon Monoxide — Carbon 
Dioxide — Carbonates — Compounds of Carbon, with Hydrogen — Nitrogen — 
The Atmosphere — Ammonia— Ammonium Salts — Oxides and Acids of Nitro- 
gen — Nitric Acid— Nitrates — Nitrous Acid and Nitrites— Sulphur— Sul- 
phuretted Hydrogen — Sulphur Dioxide — Sulphurous Acid and Sulphites — 
Sulphuric Acid and Sulphates — Bromine, Iodine, and Fluorine— Silicon, 
Silica, and Silicates — Phosphorus, Phosphoric Acid, and Phosphates — Metals 
and their Compounds — Calcium and its Compounds — Potassium and its 
Compounds — Sodium Compounds. 

CHAPTER III. 

Description op Organic Compounds. 34 

Organic Chemical Compounds — Organised Structures — Composition of Organic 
Bodies — Classification of Organic Compounds — Organic Radicals — Hydrides 
of Organic Radicals (Paraffin Group) — The Alcohols — Methyl Alcohol — 



10 Table of Contents. 



PAGE. 

Ethyl Alcohol — Detection of Alcohol — Methylated Spirits of Wine— Propyl, 
Butyl, and Amyl Alcohols — Fusel or Fousel Oil — Glycerin — The Ethers — 
Ethereal Salts — Chloroform — Iodoform — Organic Acids — Fatty Acids, or 
Acids of Acetic Series— Acetic Acid — Butyric Acid — The Higher Fatty 
Acids — Fats and Soaps, or Salts of Higher Fatty Acids — Lactic Acid — 
Succinic Acid — Tartaric Acid — Definition of Homologues, &c. — Nitrogenous 
Organic Bodies — Substitution, or Compound Ammonias — Alkaloids — Pepsin 
and Peptones. 

CHAPTER IV. 

The Microscope and Polarisation of Light. 46 

•Object of Microscope — Description of Microscope — How to use the Microscope — 
Measurement of Microscopic Objects — The Micromillimetre — Magnification 
in Diameters — Microscopic Sketching and Tracing — Camera Lucida — Polari- 
sation of Light. 

CHAPTER V. 

Constituents op Wheat and Flour ; Mineral and Fatty Matters. 55 

Construction of Wheat Grain — Constituents of Wheat — Mineral Constituents — 
Organic Constituents ; Fatty Matters — Experimental Work —Mineral Con- 
stituents — Fat. 

CHAPTER VI. 

The Carbohydrates. 59 

Definition of Carbohydrates — Cellulose — Occurence and Physical Properties — 
Behaviour with Chemical Reagents — Existence in Wheat — Composition — 
Starch— Occurrence — Physical Character — Microscopic Appearance — Micro- 
scopic Characters of Various Starches — Wheat — Barley — Rye — Oats — 
Maize — Rice — Potatoes— Canna Arrowroot, or Tous les Mois — Solubility of 
Starch — Action of Caustic Alkalies on Starch — Action of Zinc Chloride — 
Properties of Starch in Solution — Preparation and Manufacture of Starch — 
Dextrin — Occurrence — Physical Character — Preparation — Chemical Charac- 
ters — The Sugars — Maltose, Cane Sugar, Milk Sugar, and Glucose — General 
Properties — Maltose — Cane Sugar — Milk Sugar — Glucose or Grape Sugar — 
Dextrose or Dextro- glucose — Loevulose or Lcevo-glucose — Commercial 
Glucose — Malto-dextrin — Experimental Work —Cellulose— Microscopic Ex- 
amination of Starches — Examination of Mixed Starches — Gelatinisation of 
Starch — Action of Caustic Alkalies and Zinc Chloride on Starch — Reactions of 
Starch Solution — Dextrin — Maltose and other Sugars. 

CHAPTER VII. 

Transformation of the Carbohydrates. 75 

Hydrolysis — Hydrolytic Agents — Diastasic Action or Diastasis — Saccharification 
— Saccharification of Starch by Acids — Action of Diastase on Starch — Brown, 
Heron and Morris' Researches — Malt Extract employed — Action of Malt 
Extract on Cane Sugar— On Ungelatinised Starch — On Bruised Starch — 
Upon Starch Paste in the Cold — On Starch Paste at Higher Temperatures — 
Molecular Constitution of Starch, Dextrin, and Maltose — Details of 



Table of Contents. 11 

PAGE. 

Hydrolysis — Empirical Statement of Hydrolysis of Starch — Hydrolysis of 
Cane Sugar — Of Dextrin — Of Malto-Dextrin— Of Maltose — Saccharin cation of 
Malt during the Mashing Process — Mashing Malt together with Unmalted 
Grain — Conditions inimical to Diastasis — Experimental Work— Hydrolysis 
of Starch — Of Cane Sugar — Mashing of Malt — Substances inimical to 
Diastasis. 

CHAPTER VIII. 

Albuminoids or Proteids. 85 

List of Albuminoids — Composition of Albuminoids— Egg Albumin — Blood Albu- 
min — Vegetable Albumin — Legumin or Vegetable Casein — Soluble Albu- 
minoids of Wheat — Insoluble Albuminoids of Wheat, Gluten — Composition 
of Gluten — Glutin, Gliadin, or Vegetable Gelatin — Mucin or Mucedin — 
Vegetable Fibrin or Insoluble Albumin — Mutual Relations of Glutin, Mucin, 
and Vegetable Fibrin — Non-existence of Gluten as such in Flour — Cerealin 
— Putrefaction and its Relation to Diastasis — Diastase — Experimental 
Work — Soluble Albuminoids— Gluten and its Constituents. 



CHAPTER IX. 

Fermentation. 95 

Origin of Term — History of the Views held of the nature of Fermentation — 
Definition of Fermentation — Modern Theory of Fermentation — Experimental 
Basis of Modern Theory — Varieties of Fermentation —Alcoholic Fermenta- 
tion and Yeast — Substances susceptible of Alcoholic Fermentation — 
Fermentation viewed as a Chemical Change — Chemical composition of Yeast 
— Yeast as an Organism— Botanic position of Yeast — Varieties of Yeast — 
Saccharomyces Cerevisice, or ordinary Yeast — High Yeast — Life History — 
Influence of Temperature on Yeast Growth — Substances necessary for the 
Nutriment of Yeast — Saccharine Matters— Nitrogenous Nutriment — Mineral 
Matter necessary for the Growth of Yeast — Insufficiency of either Sugar or 
Nitrogenous Matter only for the Nutriment of Yeast — Behaviour of Free 
Oxygen to Yeast — Malnutrition of Yeast — Reproduction of Yeast, other 
than by Budding— Substances inimical to Alcoholic Fermentation — Low 
Yeast — Distinctions between High and Low Yeast — Low Yeast not used for 
Breadmaking — Convertibility of Low and High Yeasts— Methods for the 
Isolation of Yeast and other Organisms — Pasteur's " New High Yeast " — 
Saccharomyces Minor — Saccharomyces Ellipsoideus — Saccharomyces Pas- 
torianus — Saccharomyces Mycoderma, or Mycoderma Vini — Saccharomyces 
Albicans— Experimental Work — Substances produced by Alcoholic Fer- 
mentation — Microscopic Study. 

CHAPTER X. 

Lactic and Putrefactive Fermentation. 123 

Schizomycetes — Bacteria — Bacterium Termo — Bacilli — Bacillus Subtilis — Lactic 
Fermentation — Diastasic action of Bacteria — Viscous Fermentation — Butyric 
Fermentation — Putrefactive Fermentation — Action of Oxygen on Bacterial 
and Putrefactive Ferments — Conditions inimical to Putrefaction — Products 
of Putrefaction — Disease Ferments — Spontaneous Fermentation — Experi- 
mental Work. 



12 Table of Contents. 



CHAPTER XI. 

Technical Reseaeches on Fermentation. 13$ 

Strength of Yeast — Yeast Testing Apparatus — Degree of Accuracy of Method — 
Constancy of Strength of same Yeast— Effects of different Media on Yeast 
Growth— Comparison between Sugar, Yeast Mixture, Pepsin, and Albumin — 
Comparison between Filtered Flour Infusion, Wort, and Yeast Mixture Solu- 
tion — Comparison between Flour and its various Constituents fermented 
separately — Further investigation of Fermentation of Flour Infusion — 
Effect of Salt on the Fermentation of Flour — Effect on Fermentation of 
addition of various Substances to Yeast Mixture — Effect on the Fermentation 
of Sugar of the addition of Flour and Potatoes — Effect of Temperature on 
Fermentation — Result of using different Quantities of Yeast — Further Com- 
- parisons of Fermentation in Flour and Sugar Solutions — Experimental 
Work — Apparatus Requisite — Automatic Temperature Regulator — Method 
of Testing — Preparation of Yeast Mixture — Keeping Properties of different 
Yeasts — Use of Testing Apparatus without Temperature Regulator. 



CHAPTER XII. 

Manufacture and Strength of Yeasts. 182 

Brewers' Yeast — Microscopic Examination of Yeast — Manufacture of Com- 
pressed Yeasts — " Patent," or Bakers' Home-made Yeasts — Bakers' Malt 
and Hop Yeasts— Patent Yeast Recipes — Virgin Malt Yeast, Haig's "Patent" 
— Banbury Patent Yeast — Patent Yeast, Feaist's Formula — Suggestions on 
Yeast Brewing ; what to do, and what to avoid — Specific Gravity of Worts and 
Attenuation — Microscopic Sketches of Patent Yeast — Scotch Flour Barms 
— Thorn's Formulae — Virgin Barm — Things Required — How to use them — 
Fermentation — Parisian Barm — " Glasgow Bakers'" Formula — Ingredients — 
Mode— Suggested Modification of Flour-Barm Recipes — Microscopic Charac- 
ter — Strength of various Yeasts — First Series— Second Series. 



CHAPTER XIII. 

Moulds and Fungoid Growths. 21 3"' 

Mycoderma Aceti — Penicillium Glaucum — Aspergillus Glaucus — Mucor Mucedo 
— Micrococcus Prodigiosus — Musty and Mouldy Bread — Diseases of Cereals 
— Mildew — Smut — Brefeld on Identity of Smut and Yeast — Bunt or Stink- 
ing Rust— Ergot. 

CHAPTER XIV. 

Physical Structure of the Wheat Grain. 

Longitudinal Section of Whole Grain — Transverse Section of Grain — Section 
Cutting and Mounting — The Germ — Endosperm and Bran — Bran Cellulose — 
Cellulose of Endosperm. 



Table of Contents. 13 



CHAPTER XV. 

Chemical Composition of Wheat. 233 

Principal Constituents of Cereals — Fat— Starch — Cellulose — Dextrin and Sugar 
— Soluble Albuminoids — Soluble Extract — Insoluble Albuminoids, Gluten — 
Ash — Water — Analyses of English and Foreign Wheats — Average Com- 
position of American Wheats. 



CHAPTER XVI. 

Chemical Composition of Flour and other Milling Products. 245 

■Colour — Strength — Strength Burette — The Viscometer — Outline of Method em- 
ployed in Viscometric Determinations — Results of Viscometric Strength 
Determinations — Composition of Roller Milling Products — Explanation of 
Diagram — Tailings — Break Flours — Middlings and Semolinas — Flours — Offals 
— Fine Sharps — Coarse Sharps — Rolled Sharps — Bran — Fluff — The Germ — 
Richardson's Analyses of Products of Roller Milling— Interpretation of the 
Analyses — Further Examination of Flours produced during Gradual 
Reduction — Damping Wheats — Artificial Drying of Wheats and Flours — 
General Relationship existing between Strength, Gluten, Moisture, and 
Colour of Flours — Effect of the Germ on Flour — Wheat Blending — Distri- 
bution of Gluten in Wheat — Tabulated Results of Flour Analyses. 



CHAPTER XVII. 

Bread Making. 305 

Salt — Water — Objects of Breadmaking — Description of various Processes of 
Breadmaking — The Ferment — The Sponge— The Dough — London Practice — 
Bennett's Account — Bischof's Methods with Compressed Yeast — Method 
without Ferment — With Ferment — Birmingham Practice — Manchester Prac- 
tice — Scotch Practice — Half Sponge — Quarter Sponge — Doughing and 
Baking — Review of Panary Fermentation — The Ferment — Panary Fermenta- 
tion — Sponging and Doughing — Variety and Quantity of Yeast used — 
Management of Sponging and Doughing — Use of Salt — Loss during Fer- 
mentation — Baking — Time necessary for Baking— Glazing— Solid and Flash 
Heats— Cooling of Bread— Souring of Bread — Sanitary Aspects of Bakehouses 
— Remedies for Sour Bread — Working with Unsound or very Low Grade 
Flours — Use of Alum, Copper Sulphate, and Lime^-Special Methods of 
Breadmaking — Vienna Bread — Leavened Bread— Other Theories of Panary 
Fermentation — Mege Mouries— Recent Researches by Chicandard — Methods 
of Aerating Bread other than by Yeast — Baking Powders — Self-Raising Flour 
— Use of Hydrochloric Acid — Whole Meal Bread — The Aeration Process — 
Gluten Bread — Relative Nutritive Values of different varieties of Bread — 
Unsuitability of Barley Meal, &c, for Breadmaking — Wheat and Flour 
Blending. 



lJf Table of Contents. 



CHAPTER XVIII. 

Modern Baking Machinery and Appliances. 342 

Sanitary, Financial, and "Working Considerations — Classification of Machinery — 
Ferment Treating Machinery — Flour Sifting Machines — Baker's Flour Sifter 
— Pfleiderer's Flour Sifter — Sponge Stirrers — Kneading Machines — 
Pfleiderer's Doughing Machine— " Thomson " Kneading Machine — Melvin's 
Kneading Machine — " Drum " Kneading Machine — Killing or Felling of 
Dough — Cleaning Doughing Machines — Ovens — Bailey-Baker Oven — Mason 
Continuous Baking Hot- Air Oven — Steam Ovens — Thompson's Gas Oven — 
Bakers' Patent Oven Light — Author's Personal Opinions on Ovens and 
Machines. 



CHAPTER XIX. 

Analytic Apparatus. 367 

Commercial Testing and Chemical Analysis of Wheats and Flours — The Labora- 
tory — The Analytical Balance — Adjustment of Balance — Analytic Weights — 
Operation of Weighing — Apparatus employed for Measuring Purposes — 
Burettes and Floats — Pipettes— Measuring Flasks. 

CHAPTER XX. 

Commercial Testing of Wheats and Flours. 378 

Importance of Commercial Testing — Principles of — Practicability of — Commercial 
Assay of Wheat — Weight per Bushel — Weight of 100 Grains — Grinding of 
Samples — Strength — Strength Burette — Testing with Viscometer — Stability 
Tests — Gluten Testing — The Aleurometer — Hot- Water Oven — Desiccator — 
Interpretation of Gluten Results — Estimation of Moisture — Baking Tests. 

CHAPTER XXI. 

Determination of Mineral and Fatty Matters in Wheats and Flours. 403 

Determination of Ash — Determination of Phosphoric Acid, and Potash in Ash — 
Phosphoric Acid Estimation — Molybdic Solution — Magnesia Mixture —Mode 
of Analyses — Washing and Ignition of Precipitates — Weight of Filter Ash — 
Potash Estimation — Counterpoised and Weighed Filters — Determination of 
Fat — Rectification of Petroleum Spirit — Soxhlett's Extraction Apparatus — 
Treatment of Ethereal Solution — Simpler Form of Extraction Apparatus. 

CHAPTER XXII. 

ACIDIMETRY AND ALKALIMETRY. 416 

Explanation of Terms — Normal Solutions ; Sodium Carbonate — Indicators : 
Litmus and Phenophthalien — Normal Sulphuric Acid — Normal Sodium 
Hydrate — Decinormal Solutions — Water, free from Carbon Dioxide. 



Table of Contents. 15 



CHAPTER XXIII. 

Soluble Extract, Acidity, and Albuminoids. 420 

Soluble Extract — Water-Bath — Soluble Extract, continued — Acidity of Meals or 
Flours — Estimation of Albuminoids by Combustion Process — Materials 
Required — Soda-lime — Asbestos — Combustion Furnace — Iron Combustion 
Tubes — U-Tube — Description of the Analysis — Estimation of Albuminoids 
by the Ammonia Process — Principle of Ammonia Process — Nessler's Solution 
— Distilled Water, free from Ammonia — Standard Solution of Ammonium 
Chloride — Alkaline Permanganate Solution — Apparatus Required — Method 
of making the Analysis — Comparison between Combustion and Ammonia 
Processes — Estimation of Total Albuminoids — Modification of Combustion 
Process for Estimation of true Albuminoids only. 



CHAPTER XXIV. 

Estimation of Carbohydrates. 438 

Estimation of Sugar by Fehling's Solution — Fehling's Standard Copper Solution 
— Alkaline Tartrate Solution — Action of Sugars on Fehling's Solution — 
Gravimetric Method on Cane Sugar — Volumetric Method on Cane Sugar — 
Estimation of Maltose in Wheats or Flours — Estimation of Dextrin — Polari- 
metric Estimations — Specific Rotatory Power — The Polarimeter — Polarimeter 
Tubes — Polarimeter Tube, with Thermometer — Verification of Zero of Polari- 
meter — Method of Reading with Vernier— Polarimetric Estimation of Cane 
Sugar — Polarimetric Behaviour of Inverted Cane Sugar — Polarimetric 
Determination of Dextrin and Maltose — Estimation of Starch — Estimation of 
Soluble Starch by conversion into Dextrin and Maltose — Alcohol — Diastase 
— Method of Performing Analysis — Estimation of Cellulose — Special Reagents 
necessary — Mode of Analysis. 



CHAPTER XXV. 

Bread Analysis. 457 

Colour— Texture — Piling — Odour — Flavour — Colour and Thickness of the Crust 
— Quantity of Water in Bread — Analytic Estimations — Moisture — Ash — 
Acidity — Fat. 

CHAPTER XXVI. 

Adulteration. 463 

Standard Works on the Subject— Information derived from Normal Analysis — 
Impurities and Adulterants of Flour — Darnel — Ergot and Mould — Mineral 
Adulterants — Chloroform Test — Special Test for Alum — Alum in Bread. 



THE CHEMISTRY, 

THEORETICAL AND PRACTICAL, 

OF 

WHEAT, FLOUR, AND BREAD. 

CHAPTER I. 

INTRODUCTORY. 

1. General Scope Of Work. — The Chemistry of Wheat, Flour, 
and Bread is so closely associated with certain other departments of 
science as to render their separation from each other almost impossible. 
Thus, in order that the chemical composition of a grain of wheat be 
understood, it is also necessary that the student shall be familiar with 
its physical structure. The changes which occur during fermentation 
cannot be mastered without a knowledge of the life-history of yeast and 
certain other organisms. In addition, therefore, to the purely chemical 
treatment of the subject, this work will comprise such references to the 
cognate sciences of botany and biology as will be of service to the 
miller, baker, and others concerned in the production and manipulation 
of flour. In compliance with a widely -expressed wish, a chapter will 
be devoted to a description of modern baking machinery and appliances 

2. Definition of Chemistry. — Chemistry has well been denned 
as that science which treats of the composition of matter, of changes 
produced therein by certain natural forces, and of the action and 
reaction of different kinds of matter on each other. It follows that the 
Chemistry of "Wheat, Flour, and Bread may be denned as that 
branch of the science which treats of the composition of these 
bodies, of the changes they undergo when subjected to the 
action of certain natural forces, and of the action and reaction 
of these and other kinds of matter on each other. 

3. Study of General Chemistry necessary. — An elementary 

course of study of the general principles of chemistry must precede that 
of any particular branch of the applied science. Such a course should 
include the preparation and properties of the commoner elements and 
their compounds, the principles of qualitative analysis, and the simpler 
laws governing chemical action and combination. Technical students 
attending the author's lecture and laboratory classes use for this pur- 
pose, as an introductory text-book, "Jago's Elementary Chemistry, 

B 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



Theoretical and Practical," published by Messrs. Longmans & Co. For 
convenience of reference, a short description follows of the most impor- 
tant chemical laws, and also of such elements and compounds as are 
closely connected with the chemistry of wheat, flour, and bread. This 
brief account must not, however, be accepted as a substitute for a 
systematic course of study of elementary chemistry. 

4. Important Preliminary Statements and Definitions.— 

Chemical changes are often accompanied by very great alterations in 
the appearance and properties of the bodies involved ; for example, 
when a candle is burned it almost entirely disappears, but although it 
no longer remains in the solid state, the whole of its constituents exist 
as gases, and these weigh exactly the same as did the candle, plus the 
oxygen of the air with which it has combined. Matter is indestruc- 
tible, and, consequently, the same weight of material remains 
after any and every chemical change as there was before its 
commencement. 

It is important that at the outset accurate and concise ideas are 
gained of the meaning of various chemical terms. Although matter- 
assumes so many diversified forms, yet all bodies, on being subjected to 
chemical analysis, are found to consist of one or more of a class of 
between sixty and seventy substances, which are termed "elements." 

An Element is a substance which has never been separated 
into two or more dissimilar substances. 

While the letters of the alphabet are few, the number of words 
which can be formed from them is practically infinite ; so, in a some- 
what similar fashion, from the comparatively small number of elements 
which constitute the " alphabet " of chemistry, there may be built up an 
immense number of chemical compounds. 

A Compound is a body produced by the union of two or more 
elements in definite proportions, and, consequently, is a sub- 
stance which can be separated into two or more dissimilar 
bodies. Compounds differ in appearance and characteristics from their 
constituent elements. 

The term " Mixture " is applied to a substance produced by 
the mere blending of two or more bodies, elements or com- 
pounds, in any proportion, without union. Each component of 
a mixture still retains its own properties, and separation may be effected 
by mechanical means. 

5. List Of Elements. — The following is a list of some of the more 
important elements, together with their symbols and other particulars : — 

Name. 

Aluminium, 
Barium, 
Boron, 
Bromine, - 
Calcium, - 
Carbon, - 
Chlorine, 



Symbol. 

Al 


Combining or 

Atomic Weight. 

Old. Mew. 

27 27-3 


Atomicity. 
IV 


Ba 


137 


136-8 


II 


B 


11 


11-0 


III 


Br 


80 


79-75 


I 


Ca 


40 


39-9 


II 


C 


12 


11-97 


IV 


CI 


35-5 


35-37 


I 








INTRODUCTORY. 




3 


Name. 

Chromium, 


Symbol. 

Cr 


Combining or 

Atomic Weight. 

Old New. 

52-5 52-4 


Atomicity. 
VI 


Copper (Cuprum), 
Fluorine, 
Hydrogen, 
Iodine, 


Cu 
F 
H 
I 


63 

19 

1 

127 


63-0 

19-1 

1-0 

126-53 


II 

I 
I 


Iron (Ferrum), - 


Fe 


56 


55-9 


VI 


Lead (Plumbum), - Pb 
Magnesium, - - Mg 
Manganese, - - Mn 
Mercury (Hydrargyrum), Hg 
Nitrogen, - - N 


206 
24 
55 

200 
14 


206-4 
23-94 
54-8 

199-8 
14-01 


IV 

II 

VI 

II 

V 


Oxygen, - 





16 


15-96 


II 


Phosphorus, 


P 


31 


30-96 


V 


Platinum, - 


Pt 


197 


196-7 


IV 


Potassium, 


K 


39 


39-04 


I 


Silver (Argentum), 
Silicon, - 


Ag 

Si 


108 

28 


107-66 

28-0 


I 

IV 


Sodium (Natrium), - 


Na 


23 


22-99 


[ 


Sulphur, - 


S 


32 


31-98 


VI 


Tin (Stannum), - 


Sn 


118 


117-8 


IV 


Zinc, 


Zn 


65 


64-9 


II 



6. Metals and Metalloids. — The elements are divided into two 
groups, termed respectively "Metals," and "Metalloids" or non-metals. 
The non-metals are distinguished in the foregoing table by being printed 
in small capitals. The line of division between the two classes is not 
very marked, the one group gradually merging into the other. The 
metals, as a class, are opaque bodies, having a peculiar lustre known as 
metallic ; they are usually good conductors of heat and electricity. 
Two of the elements, mercury and bromine, are liquid at ordinary tem- 
peratures, while hydrogen, oxygen, nitrogen, and chlorine are gaseous. 

7. Symbols and Formulae. — The symbols are abbreviations of 
the names of the elements, and, where practicable, consist of the first 
letter of the Latin names. When two or more elements have names 
commencing with the same letter, it becomes necessary to distinguish 
tnem from each other by restricting the initial letter to the most im- 
portant element, and selecting two letters as the symbol of each of the 
others. Thus, carbon and chlorine each commence with " C," that 
letter is chosen as the symbol of carbon, while that of chlorine is CI. 

As all compound bodies consist of elements united together, they may 
be conveniently expressed symbolically by placing side by side, the 
symbols of the constituent elements : the symbol of a compound is 
termed its formula. Thus, common salt consists of chlorine and 
sodium ; its formula is accordingly written, NaCl. 

8. Further uses of Symbols and Formulae : law of 

Chemical combination by weight. — Simply as abbreviations of 
the full names, symbols and formulae are of great service ; this, however, 
is but a small part of their significance and value to the chemist. Their 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



further use may best be explained by reference to certain information 
gained by experiment, to which careful attention is requested. On 
analysis, it is found that 36*5 ounces of the substance known as hydro- 
chloric acid consist of 1 ounce of hydrogen, combined with 35-5 ounces 
of chlorine; also, that in 58*5 ounces of common salt there are 35 - 5 
ounces of chlorine to 23 of sodium. Taking water as another instance 
of a hydrogen compound, analysis shows that its composition may be 
expressed by the statement that, 1 8 ounces of water consist of 2 ounces 
of hydrogen combined with 16 ounces of oxygen. In the table given 
on page 2 there is a column, headed " Combining or Atomic Weight;" 
on referring to this it will be found that the numbers opposite hydrogen, 
chlorine, sodium, and oxygen, are, respectively, 1, 35*5, 23, and 16, being 
(with one exception) identical with those that have just been given as 
the numbers obtained by analysis of the compounds under consideration. 
It is possible to assign to every element a number, which 
number, or its multiple, shall represent the proportionate 
quantity by weight of that element which enters into any 
chemical compound. These numbers are termed the " Com- 
bining or Atomic Weights " of the elements, and are deduced 
from results obtained on actual analysis. In addition to its use 
as an abbreviated title of any element, the symbol represents the 
quantity of the element indicated by its combining weight ; 
where multiples of that quantity exist in a compound, the fact is ex- 
pressed by placing a small figure after the symbol and slightly below 
the line. In the table of elements, there are two columns of combining 
weights given, headed respectively " Old " and " New ; " the second 
column gives those obtained by Stas as a result of recent researches. 
For most purposes the weights given in the first column are sufficiently 
accurate. 

As previously stated, the formula of sodium chloride is NaCl, and it 
contains 23 of sodium to 35-5 of chlorine. The formula of hydrochloric 
acid is HC1, and it contains 1 of hydrogen to 35*5 parts of chlorine. 
Water consists of 2 parts of hydrogen to 1 6 of oxygen ; the fact that it 
contains twice the combining weight of hydrogen is expressed by writing 
the formula, H 2 0. Again, ammonia contains 3 parts by weight of 
hydrogen to 14 parts of nitrogen, consequently it has the formula, NH 3 : 
the substance commonly termed carbonic acid gas consists of 32 parts, 
or twice the combining weight, of oxygen to 1 2 by weight of carbon, the 
formula is consequently C0 2 . The quantity of an element, repre- 
sented by its combining weight, is termed " one combining 
proportion " of that element. 

9. Constitutional Formulae.— In addition to simply showing 
the number of atoms of each element present, formulae are frequently 
so written as to show the probable constitution of the molecule j such 
formulae are termed " Constitutional Formulae." 

10. Chemical Equations. — Chemical changes are most con- 
veniently expressed by what are termed "chemical equations:" these 
consist of the symbols and formulas of the bodies participating, placed 
before the sign = , while those of the resultant bodies follow. As an 



INTRODUCTORY. 



instance it may be mentioned that, when a solution of potassium iodide 
is added to one of mercury chloride, potassium chloride and mercury 
iodide are produced. The equation representing this chemical action 
is written thus : — 

2KI + HgCl 2 = 2KC1 + Hgl 2 . 

Potassium Iodide. Mercury Chloride. Potassium Ch'oride. Mercury Iodide. 

Having access to a table of combining weights, the chemist learns 
from this equation that two parts of potassium iodide, each containing 
-one combining proportion of potassium weighing 39, and one of iodine 
weighing 127, together with one part of mercury chloride, containing 
one combining proportion of mercury, weighing 200, and two of chlorine, 
each weighing 35 -5; together yield or produce two parts of potassium 
chloride, each consisting of one combining proportion of potassium, 
weighing 39, ami one of chlorine, weighing 35 "5 ; and one part of mer- 
cury iodide, containing one combining proportion of mercury weighing 
200, and two combining proportions of iodine each weighing 127. As 
no chemical change affects the weight of matter, the weight of the 
quantity of a compound, represented by its formula, must be the sum 
of that of the constituent elements : so, too, the weight of the bodies 
resulting from a chemical change must be the same as that of the bodies 
before the change, whatever it may be, had occurred. Although from 
a chemical equation and table of combining weights, it is possible to 
state what relative weight of each element is concerned in any chemical 
action, it must never be forgotten that the combining weights were 
first determined by experiment and then the table compiled 
therefrom. The statement of premise and deduction is that hydrogen 
and chlorine have respectively the combining weights of 1 and 35 - 5 
.assigned to them, because analysis shows that they combine in those 
proportions : not that hydrogen and chlorine have as combining 
weights 1 and 35*5, and therefore they must combine in those pro- 
portions. The combining weights are simply a tabular expression of 
results obtained by practical analytic investigation. This cannot be too 
strongly insisted on ; ask many a young chemical student how it is 
known that hydrochloric acid consists of 1 by weight of hydrogen and 
35 *5 of chlorine, and he will answer "because these are the combining 
weights of the elements." Ask him how it is known that 1 and 35-5 
are the combining weights of hydrogen and chlorine, and he will not 
have the slightest idea that they are simply deductions from experi- 
mentally obtained results. For this state of things many of the older 
text-books are largely responsible. 

11. Atoms and Molecules. — The fact that the quantity of every 
element which enters into combination is either a certain definite and 
unchangeable weight, or a multiple of that weight, led chemists to feel 
that this weight of a combining proportion of an element is in some 
way associated with its physical nature. The first step toward the 
explanation of this question is due to Dalton, who enunciated what is 
termed the Atomic Theory. He assumed that all matter is built up of 
extremely small particles, which are indivisible, and that when elements 
combine, it is between these particles that the act of union occurs. 
These ultimate particles of matter are termed " Atoms." The name 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



" atom " is derived from the Greek, and signifies that which is indivisi- 
ble. Atoms of the same element are supposed to be of the same size 
and weight. With the absolute weight of atoms the chemical student 
has but little to do : the principal point of importance for him is their 
relative weights compared with each other. For chemical purposes, an 
atom may be denned as the smallest particle of an element 
which enters into, or is expelled from, a chemical compound. 
For the phrase, "combining proportion," hitherto used, the 
term "Atom" may be substituted; the combining weight 
then becomes the relative weight of the atom of each element, 
compared with that of hydrogen, which, being the lightest, is 
taken as unity. Though the atomic theory does not admit of absolute 
proof, yet it so amply and consistently explains all the phenomena of 
chemistry that its essential principles are universally recognised. 

The little group of atoms represented by the formula of a compound 
is termed a "molecule." A molecule is the smallest possible par- 
ticle of a substance which can exist alone. In the case of 
chemical compounds, the molecule cannot be further subdivided, except 
by separation into the atoms of its constituent elements, or into two or 
more molecules of some simpler chemical compound or compounds. 
When elements are in the free or uncombined state, their atoms usually 
combine together to form elementary molecules, thus in oxygen, two 
atoms unite to form a molecule of oxygen ; the formula of the oxygen 
molecule is written, 2 . 

The molecules of the following elements contain two atoms — hydro- 
gen, chlorine, oxygen, sulphur, and nitrogen. 

As all elements normally exist in the molecular state, it is advisable 
to always use equations in which the lowest quantity of any element 
present is a molecule. Thus, H 2 + Cl 2 = 2HC1, should be written as the 
equation representing the combination of hydrogen and chlorine, rather 
than, H + C1 = HC1. 

12. Measures of Weight and Volume.— It will be conveni- 
ent to furnish a statement of the different systems of weights and 
measures usually employed for scientific purposes. The chemist, as a 
rule, prefers the metric system, as in common use in France, to the 
very complicated system of weights and measures employed in this 
country. One reason is that the metric system is extremely simple ; 
another, that the measures of weight and volume are directly connected 
with each other. If the writer simply followed his own predilections, 
metric weights and measures only would be used throughout this work, 
but it having been strongly represented to him that the introduction of 
the English equivalents of the different weights employed would be a 
help to some of his readers, they also have been, in all cases, given. 
The writer is conscious that the result of this intermixture is often in- 
congruous, but to those familiar with the metric system this will present 
no difficulty, while to those who are unacquainted with it, it will be an 
assistance. It is nevertheless urged that the metric system be mas- 
tered ; this may be easily done in a quarter of an hour, much time will 
then be saved which otherwise would have to be spent in making 
calculations. 






INTRODUCTORY. 



13. The Metric System. — The unit of the metric system is a 
"metre" which is the length of a rod of platinum that is deposited in 
the archives of France. The metre measures 39-37 English inches. The 
higher and lower measures are obtained by multiplying and dividing by 
10, thus :— 

Kilometre =1000 metres = 39370 inches. 
Hectometre = 100 „ = 3937-0 

Decametre = 10 „ = 393-70 

Metre = 39-370 „ 

Decimetre = 0*1 metre = 3*937 „ 

Centimetre = 001 „ = 0-3937 inch. 

Millimetre = 0-001 „ = 0-03937 „ 

In the above, and all other measures of the metric system, the prefixes 
"kilo, hecto, and deca" are used to represent 1000, 100, and 10 respec- 
tively ; and " deci, centi, and milli," to represent a tenth, hundredth, 
and thousandth. The decimetre is very nearly 4 inches in length, and 
the millimetre very nearly one twenty-fifth of an inch : remembering 
this, measures of the one denomination can be roughly translated into 
those of the other. The exact length of a decimetre is shown in Fig. 1. 



Each side of this square measures 

i Decimetre, or 
IO Centimetres, or 
ioo Millimetres, or 
3*937 English inches. 

A litre is a cubic measure of I decimetre in the side, or a cube 
each side of which has the dimensions of this figure. 

When full of water at 4 C. a litre weighs exactly 1 kilogram or 
1000 grams, and is equivalent to 1000 cubic centimetres ; or to 
61*024 cubic inches, English. 

A gram is the weight of a centimetre cube of distilled water; at 
4 C. it weighs 15 432 grains. 



1 sq. 
Centim. 



-3 



— 10 



4 inches. 
Fig. 1. 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



The unit of the measure of 


capacity is the " litre," which is the 


volume of a cubic decimetre : — 








Cubic Inches. 


Pints. Fluid ounces. 


Kilolitre =1000 litres = 


61027 


1760-7 35214 


Hectolitre = 100 


6102-7 


176-07 3521-4 


Decalitre = 10 „ = 


610-27 


17-607 352-14 


Litre! = 


61-027 


1-7607 35-214 


Decilitre = 0*1 litre = 


6-1027 


0-17607 3-5214 


Centilitre = 0*01 „ = 


0-6102 


0-017607 0.3521 


Millilitre = 0.001 .. = 


0-06102 


0-00176 0-0352 



The decimetre being 10 centimetres in length, it follows that a cubic 
decimetre must be equal to 1000 cubic centimetres, and that the milli- 
litre has a volume of a cubic centimetre. The name " cubic centimetre," 
or its abbreviation " c.c." is almost always used in preference to 
millilitre ; thus a burette or pipette is said to deliver 50 c.c., while a 
litre measure is often termed a " 1000 ex." measure. 

A cubic inch is equal to 16.38 cubic centimetres. 



The unit of the measure of weight is the 



gramme, or 



this 



is the weight of a cubic centimetre of distilled water at its maximum 



density (4° C. =39-2° F.) :— 



Kilogram 

Hectogram 

Decagram 



= iooo 

= 100 
- 10 



Gram 

Decigram = 

Centigram — 

Milligram = 



0-1 gram 
0-01 „ 
0-001 „ 



Grains. 

15432-3 
1543-23 
154-323 
15-4323 
1-54323 
0-15432 
0-01543 



Avoirdupois onnces. 

35-2739 
3-52739 
0-35273 
0-03527 
0-00352 
0-00035 
0-000035 



si 



A kilogram is just over 2 lbs. 3 \ oz., and a hectogram is very nearly 
oz. An ounce avoirdupois equals 28-35 grams. 

The relation between the weight and volume of water is a very 
simple one ; the volume being the same number of c.c. as the weight is 
grams. With other liquids the volume in c.c. x specific gravity = 
weight in grams. 

14. English Weights and Measures. — Familiarity with Eng- 
lish weights and measures is assumed, still the following particulars will 
most likely be of service — one gallon of pure water at a temperature of 
62° F. (16-6° C.) weighs 10 pounds or 160 ounces or 70,000 grains; the 
pint, therefore, weighs 20 ounces. The measure termed a " fluid ounce " 
is derived from the weight of a pint of water. A fluid ounce is a 
measure of volume, not of weight, and equals one-twentieth part of a 
pint. The fluid ounce bears the same relation to the avoirdupois ounce, 
as does the cubic centimetre to the gram. A gallon is equal to 277-274 
cubic inches. An ounce avoirdupois weighs 437 -5 grains. 

15. Heat Measurements. — The most important measures of 
heat are its temperature, or intensity ; and quantity. 

16. Temperature. — The temperature of a body is a measure 
of the intensity of its heat, and is further denned as the 



INTRODUCTORY. 9 



thermal state of a body considered with reference to its power 
of communicating heat to other bodies. Temperature is, in fact, 
the measure of what is popularly termed " how hot a body is ; " it will 
be seen on consideration that this depends on the power the body has 
of imparting heat to another body. Thus, if when the hand is thrust 
into water, the water is able to yield heat to the hand, it is said to be 
" hot," while if it robs the hand of heat it is said to be " cold." 

17. The Thermometer. — The instrument used for measuring 
temperature is termed a "thermometer." The thermometer consists of 
a glass tube of very narrow bore, with a bulb blown at the end ; the 
bulb and part of the tube are filled with mercury, all the air is then 
driven out, and the tube hermetically sealed by fusing its upper end. 
The thermometer is placed in contact with any body whose temperature 
it is desired to measure ; if the body be the colder of the two the ther- 
mometer yields heat to it, or receives heat if it be the hotter. This 
transference of heat continues until the temperature of the two is equal. 
Mercury expands with an increase, and contracts with a decrease, of 
temperature, but for the same temperature has always the -same volume. 
From the construction of the thermometer any alteration of the volume 
of the mercury is readily observed ; the height of the mercury in the 
tube is therefore a measure of its volume, and secondarily of its tempera- 
ture, and that of any body with which it is in contact. 

18. Thermometric Scales. — Subject to certain precautions, the 
temperatures of melting ice and of steam in contact with boiling water 
are constant. The height at which the mercury stands when immersed 
in each of these is marked on most thermometers ; for the registration 
of other temperatures some system of graduation must be employed. 
The one most commonly employed in this country is that of Fahrenheit, 
while for scientific purposes that of Celsius or the Centigrade Scale is 
almost universally adopted. Fahrenheit divided the distance between 
the melting and boiling-points of his thermometer into 180 degrees; 
degrees of the same value were also set off on either side of these limits. 
At 32 degrees below the melting point he fixed an arbitary zero of 
temperature, from which he reckoned. On his thermometric scale, the 
melting point is 32°, while the boiling point is 32 + 180 = 212°. Degrees 
below the zero are reckoned as — (minus) degrees, thus — 8° means 8 
degrees below zero, or 40 degrees below the melting point ; degrees 
above 212 simply reckon upwards, 213, 214° F., &c. 

The Centigrade Scale is much simpler, the melting point is taken as 
0° or zero, and the boiling point as 100°, temperatures below the 
melting point are reckoned as — degrees. 

The conversion from one to the other of the Centigrade and Fahren- 
heit Scales may be easily performed. 

180 Fahrenheit degrees =100 Centigrade degrees. 

" ii 55 — " 55 55 

1 ,, degree = 4 ,, degree. 

£ = i 

5 5) 55 x 55 55 

There is this important difference between the two scales — Centigrade 



10 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



degrees count 



degrees 



are 



from the melting point, while Fahrenheit 
reckoned from 32 below the melting point. 

30° C. = 30 x I = 54 Fahrenheit degrees. 
Therefore 30° C. are equivalent to 54 Fahrenheit degrees above the melting 
point, but as the melting point is 32, that number must be added on to 
54 ; the temperature Fahrenheit equal to 30° C. is 86°. By the reverse 
operation, Fahrenheit degrees are converted into degrees centigrade. 
The following formulae represent the two operations : — 



C°x9 



+ 32 = F°. 



(F°-32)x5 



= C°. 



The following table gives the equivalent readings on the two thermo- 
metric scales for some of the most important temperatures : — 

F. 



40° ( 


■> 


-40 


17-7 , 


= 





, 


5 = 


32 


15 , 


f = 


59 


15-5 , 


, = 


60 


20 , 


, = 


68 


21 -1 , 


= 


70 


25 , 


= 


77 


26.6 , 


f = 


80 


30 , 


= 


86 


35 . 


t = 


95 


40 , 


, = 


104 


45 , 


= 


113 


50 , 


= 


122 


55 , 


, — 


131 


60 , 


, = 


140 


65 , 


, = 


149 



70° 


C. 


= 


158° F. 


75 


5? 


= 


167 , 




80 


55 


= 


176 , 




85 


55 


= 


185 , 




90 


55 


= 


194 , 




95 


55 


= 


203 , 




100 


55 


= 


212 , 




150 


55 


= 


302 , 




200 


55 


= 


392 , 




232-2 


55 


= 


450 , 




250 


55 


= 


482 , 




260 


55 


= 


500 , 




287-7 


55 


= 


550 , 




300 


55 


= 


572 , 




316-6 


55 


= 


600 , 




350 


55 


= 


662 , 




400 


55 


= 


752 , 





19. Quantity Of Heat. — If two vessels, the one holding a pint 
the other a quart, are both filled with boiling water, the temperature of 
the water in each will be the same, but the quantity of heat will be 
double as much in the quart of water as in the pint. Quantity of 
heat is measured by the amount necessary to raise a certain 
■weight of some body from one to another fixed temperature. 
The amount of heat necessary to raise 1 gram of water from 
0° to 1° C. is termed a Unit of Heat. 

20. Expansion and Contraction of Gases. — There are cer- 
tain reasons which lead us to suppose that at a temperature of - 273° C. 
bodies would be entirely devoid of heat. This point -273° C. is 
therefore often termed the absolute zero of temperature ; and 
temperature reckoned therefrom is termed " absolute tempera- 
ture." The absolute temperature of a body is its temperature in 
degrees C + 273. All gases expand with increase, and contract with 
diminution, of temperature. The amount of expansion and contraction 
is the same for all gases between the same limits of temperature, pro- 
vided the temperature is considerably higher than that at which they 
condense to liquids. The volume of all gases is directly propor- 






INTRODUCTORY. 11 



tional to their absolute temperature. Because of this variation 
with temperature it is necessary to fix a temperature which 
shall be considered as a standard in expressing the volume of 
gas : 0° C. is commonly adopted for this purpose. 

Knowing the volume of a gas at any one temperature, its volume at 
any other may be easily calculated ; thus, a vessel was found to contain 
750 c.c. of air at 15° C. ; it is required to find its volume at the standard 
temperature. 

15°C. + 273 = 288° Absolute Temperature. 
0° C. + 273 = 273° 
As 288 : 273 : : 750 : 711 c.c. of gas at standard temperature. 

The volume of a gas is also affected by the pressure to which it is 
subjected : this variation is governed by what is called Boyle and 
Marriotte's Law — The volume of any gas is inversely proportional 
to the pressure to which it is subjected. The most important 
variations of pressure to which gases are liable are those resulting from 
the changes in pressure of the atmosphere. The height of the mercury 
column of the barometer is a direct measure of the pressure of the 
atmosphere, therefore that pressure is commonly expressed in the 
number of millimetres (m.m.,J which that column is high. For pur- 
poses of comparison it is also necessary to reduce all pressures 
to one standard ; that selected is an atmospheric pressure 
which causes the barometer to stand at 760 millimetres. 

The temperature and pressure quoted as standards for gas measure- 
ment, 0° C. and 760 m.m. are often termed normal temperature and 
pressure ; for this expression the abreviation, " N. T. P." is frequently 
used. 

21. AvOgadro'S Law. — The fact that all gases, whether ele- 
mentary or compound, expand and contract at exactly the same rate, 
when subjected to variations of temperature and pressure, has an 
important bearing on their probable molecular constitution. Their 
similarity in this respect has led to the assumption, expressed in the 
11 Law of Avogadro." — " Under similar conditions of temperature 
and pressure, equal volumes of all gases contain the same 
number of molecules." From this it follows, that at the same 
temperature and under the same pressure, the volume of any gaseous 
molecule is the same whatever may be the nature and composition of 
the gas. The density of a gas being known, its molecular weight is 
easily calculated. The density of a gas is the weight of any volume, 
compared with that of the same volume of hydrogen, measured at the 
same temperature and pressure, and taken as unity. It has already 
been stated that the molecule of hydrogen contains two atoms, its 
molecular weight, expressed in terms of its atomic weight is consequently 
2. The molecular weight of any gas is the weight of that 
volume which occupies the same space as does two parts by 
weight of hydrogen ; or is identical with the number obtained by 
doubling the density. Similar conditions of temperature and pressure 
are always understood in speaking of the comparative weights of gases. 
Conversely, as the molecular weight is the sum of the weights of the 



12 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

constituent atoms, the density of a gas may be determined from its 

formula. Thus, carbon dioxide gas has as its formula, C0 2 ; its mole- 

44 
cular weight is 12 + (16 x 2 = )32 = 44 : the density is -^- = 22. Here 

again it must be remembered that the molecular weight is primarily de- 
termined from the density, and not the density from the molecular weight. 

22. Absolute weight Of Hydrogen. — As hydrogen is taken as 
the unit of comparison for other gases, it is necessary that its absolute 
weight be determined with the greatest exactitude. Experiment has 
shown that 1 litre of hydrogen, at normal temperature and 
pressure, weighs 0*0896 gram; or 11 -2 litres weigh 1 gram. 
The student must make up his mind to remember this figure ; to quote 
Hofmann, the fact that at 0° C. and 760 m.m. pressure, 1 litre of 
hydrogen weighs 0*0896 gram, should be impressed "as it were with a 
graving tool on the memory." The weight in grams of a litre of 
any gas is its density x 0'0896. Thus, the density of carbon dioxide 
gas is 22 ; the weight of a litre is 22 x 0*0896 = 1'9712 grams. 

23. Laws of Chemical Combination by volume.— Not only 

does chemical combination follow definite laws, so far as weight is con- 
cerned, but also equally definite laws govern the proportions by volume 
in the case of gaseous bodies. For example, experiment shows that one 
volume of hydrogen unites with one volume of chlorine to form two 
volumes of hydrochloric acid gas. So, too, two volumes of hydrogen 
unite with one volume of oxygen to form two volumes of water-gas 
(steam). Again, ammonia consists of three volumes of hydrogen, 
united with one of nitrogen, to form two volumes of ammonia. The 
reactions are expressed in the following equations : — 
H 2 + 

Hydrogen. 

2H 2 + 

Hydrogen. 

3H 2 + 

Hvdrogen. 

It will be observed that in the first equation one molecule of hydrogen 
unites with one molecule of chlorine to form two molecules of hydro- 
chloric acid : the application of Avogadro's Law, therefore, teaches that 
these elements will unite in equal quantities of one volume to form two 
volumes of hydrochloric acid. In the same way, the proportions by 
volume in which chemical changes occur between gaseous 
bodies are always expressed in the equation, it being re- 
membered that all gaseous molecules occupy the same space, 
when measured at the same temperature and pressure. The 
following is a useful method of writing such equations, when the object 
is to show the proportions by volume in a chemical change in which any 



Cl 2 


= 


2HC1. 


Chlorine. 




Hydrochloric Acid 


°o 


= 


2H 2 0. 


Oxygen. 




Water. 


^ 2 


= 


2NH S . 


Nitrogen. 




Ammonia. 



gaseous body is 


involved. 




H 2 


+ 


Cl 2 


i volume. 




i volume. 


2H 2 


+ 


? 2 

i volu m e. 


2 volumes. 




3H 2 


+ 


N 2 


3 volumes. 




t volume. 



2HC1. 

2 volumes. 

2H 2 0. 

2 volumes. 

2NH 3 . 

2 volumes. 






INTRODUCTORY. 1 3 



24. Acids, Bases, and Salts. — The name acid is a familiar one 
because it is continually applied in every day parlance to anything 
which is sour. A number of bodies possess this distinction in common ; 
to the chemist, the sourness of an acid is but an accidental property, 
as, according to his definition of these bodies, substances are included as 
acids that are not sour to the taste. An acid may be defined as "a 
body which contains hydrogen, which hydrogen may be re- 
placed by a metal (or group of elements equivalent to a metal), 
when presented to the acid in the form of an oxide or hydrate. 
As a class, the acids are sour ; they are also active chemical agents : 
most acids are characterised by the property of changing the colour of a 
solution of litmus, a naturally blue body, to a red tint. Oxygen is a 
constituent of most acids. These are termed " oxy-acids." A few in 
which it is absent are termed " hydr-acids." Hydrochloric acid, HC1., 
is an example of these bodies. Most of the oxy-acids are produced by 
the union of water with an oxide — thus, oxide of sulphur and water 
form sulphuric acid : — 

S0 3 + H 2 = H 2 S0 4 

Sulphur Trioxide. Water. Sulphuric Acid. 

The oxides, which by union with water form acids, are termed 
anhydrides, or anhydrous acids. They are in most cases non-metallic 
oxides, but sometimes consist of metals combined with a comparatively 
large number of atoms of oxygen. 

A Base is a compound, usually an oxide or hydrate, of a 
metal (or group of elements equivalent to a metal), which 
metal (or group of elements) is capable of replacing the hydro- 
gen of an acid, when the two are placed in contact. The 
greater number of metallic oxides are bases. Bases, as well as acids, 
differ considerably in their chemical activity. Certain bsses are char- 
acterised by being soluble in water, to which they impart a peculiar 
soapy feel. These bases are termed " alkalies," and possess the property 
of restoring the blue colour to reddened litmus. The most important 
alkalies are sodium hydrate, IsTaHO, and potassium hydrate, KHO. 
The bases, lime, CaO, baryta, BaO, and magnesia, MgO, are more or 
less soluble in water, and also turn reddened litmus blue. They, with 
SrO, constitute the group known as the " Alkaline Earths." Hydrates 
are compounds of oxides with water, thus : — 

Na 2 + H 2 = 2NaHO. 

Sodium Oxide. Water. Sodium Hydrate. 

"When an acid and base react on each other, the body, 
produced by the replacement of the hydrogen of the acid by 
the metal of the base, is termed a Salt. Water is also produced 
during the reaction. Most salts have no action on litmus — that is, they 
do not affect the colour, whether it be red or blue. The action of acid 
and base on each other is illustrated in the following equation : — 
HC1 + NaHO = NaCl + H 2 0. 

Acid. Base. Salt. Water. 

25. Compound Radicals. — At times, a group of elements enters 
into the composition of a body, and performs functions very similar to 
those of an atom of an element. Such groups are not only found to 



14 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

form numbers of very definite compounds, but may be even transferred 
from one compound to another without undergoing decomposition. 
Groups of atoms of different elements which possess a distinct 
individuality throughout a series of compounds, and behave 
therein as though they were elementary bodies, are termed 
" Compound Radicals." 

26. Quanti valence or Atomicity. — Referring back to the 

three compounds of hydrogen mentioned in paragraph 23, it will be 
observed that one atom each of chlorine, oxygen, and nitrogen, combine 
respectively with one, two, and three atoms of hydrogen. If chlorine 
and oxygen compounds be classified and compared, it is found that 
oxygen in almost every instance combines with just double the 
number of atoms of the other element as does chlorine. The atom- 
combining power of elements varies — Quantivalence or Ato- 
micity is the measure of that combining power. Among the 
elements, hydrogen, sodium, and chlorine are characterised by the fact 
that one atom of each never combines with more than one atom of any 
other element. Their atomicity is unity, and as every other element 
forms a chemical compound with one or more of these, the atomicity of 
any element can usually be determined by observing with how many 
atoms of one of these three elements an atom of the element in question 
enters into combination. The atomicity of the different elements is 
given in the table included in paragraph 5. Elements with an atomicity 
of one are termed monads ; of two, dyads ; three, triads ; four, tetrads ; 
five, pentads • and of six, hexads. It is often convenient to express the 
atomicity of an element graphically. This is done by attaching a series 
of lines to the atom, according to its atomicity. These lines may be 
viewed as indicating the number of links or bonds with which the 
particular atom can combine with other atoms. Of the actual nature 
of the force which holds atoms together in chemical compounds, nothing 
is known : the bonds must only be viewed as indications of the number 
of such units of atom-combining power. The following are examples of 
these graphic symbols : — 

H— CI— — — — B = = = 

Hydrogen. Chlorine. Oxygen. Boron. Carbon. 

The same two elements often form a series of two or more compounds 
with each other ; under these circumstances the atomicity must vary. 
In the great majority of such compounds, the atomicity increases or 
diminishes by intervals of two — that is, the atomicity is either even or 
odd for an element throughout all its compounds. This is accounted for 
by the supposition that two of the bonds of an element may, by their 
union, mutually satisfy each other. This is not, however, invariably 
the case, as certain well marked exceptions to this rule are known. 
The highest known atomicity of an element is termed its " absolute " 
atomicity ; the atomicity in any particular compound is the " active " 
atomicity ; the absolute, less the active, atomicity is the " latent " 
atomicity. 

27. Basicity Of Acids. — In order to form salts, different acids 
require different quantities of a base : the measure of this quantity is 



INTRODUCTORY. 



15 



termed the " basicity " of the acid. The basicity of an acid depends 
on the number of atoms of hydrogen it contains that may be 
replaced by the metal of a base. In forming salts, one atom of 
hydrogen is replaced by one atom of a monad metal, two atoms of hydro- 
gen by an atom of a dyad, and so on. In the case of acids which 
contain more than one atom of replaceable hydrogen, salts are sometimes 
formed in which a part only of the hydrogen is replaced ; such salts are 
termed "acid" salts, while those in which the whole of the hydrogen is 
replaced are termed " normal " salts. The following are typical exam- 
ples of acids and the corresponding salts : — 



MONOBASIC ACID. 


DIBASIC ACID. 


TRIBASIC ACID. 


HNO3. 


H 2 S0 4 . 


H 3 P0 4 . 


Nitric Acid. 


Sulphuric Acid. 


Phosphoric Acid. 


NaN0 3 . 


Na 2 S0 4 . 


Na 3 P0 4 . 


Sodium Nitrate. 


Sodium Sulphate. 


Sodium Phosphate 




HNaS0 4 . 


Na 2 HP0 4 . 




Acid Sodium Sulphate. 


Disodic Hydrogen Phosj 


Ca(NO s ) 2 . 


CaS0 4 . 


Ca 3 (P0 4 ) 2 . 


Calcium Nitrate. 


Calcium Sulphate. 


Calcium Thosphate 



It is often convenient to view the acids in the light of their being 
compounds of the anhydrides with water : the corresponding salts may 
then be written as compounds of the bases with the anhydrides. This 
method is almost invariably employed when calculating the relative 
quantities of metals and acids in bodies when subjected to analysis. 
Subjoined are the formulae, written in this manner, of the acids and 
salts previously given as examples : — 



H 2 0, N 2 5 . 

Two Molecules of 
Nitric Acid. 

Na 2 0, N 2 5; 

Two Molecules of 
Sodium Nitrate. 



CaO, N 2 5 . 

One Molecule of 
Calcium Nitrate. 



H 2 0, S0 3 . 

Sulphuric Acid. 

Na 2 0, S0 3 . 

Sodium Sulphate. 

NaHO, S0 3 . 

Acid Sodium 
Sulphate. 

CaO, S0 3 . 

Calcium Sulphate. 



(H 2 0) 3 , P 2 6 . 

Two Molecules of 
Phosphoric Acid. 

(Na 2 0) 3 , P 2 5 . 

Two Molecules of 
Sodium Phosphate. 

(Na 2 0) 2 H 2 0, P 2 5 . 

Two Molecules of Disodic 
Hydrogen Phosphate. 

(CaO) 3 , P 2 5 . 

One Molecule of 
Calcium Phosphate. 



28. Chemical Calculations. — Most of the chemical calculations 
necessary in analytic work may be readily made by the help of chemical 
formulae and equations, together with a table of combining weights. 
The following are illustrations of some of the most important of these 
calculations. 

29. Percentage Composition from Formula. — Chemists 

usually express the results of analysis of a substance in parts per cent., so 
that in the case of a chemical compound it is often necessary to be able 
to calculate its chemical formula from the percentage composition, or con- 
versely, the percentage composition from the formula. The latter 
operation, as being the simpler, shall be first explained. It is possible 
from the formula of any body to arrive at the molecular weight of the 



16 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

compound, and the relative weight present of each element. Thus, to 
find the percentage composition of acid sodium sulphate : — 
The formula is 

Na H S 4 
23 + 1 + 32 + (16 x 4 =) 64 = 120. 
From the combining weights, given beneath each element, with their 
sum at the end, it is seen that the molecule weighs 120, and contains 23 
parts of sodium. Knowing that 120 parts contain 23, it is exceedingly 
easy to calculate the number of parts per 100, as the problem resolves 
itself into one of simple proportion : — 

As 120 : 100 : : 23 : 19*17 per cent, of sodium. 

As 120 : 100 :: 1 : 0*83 „ „ hydrogen. 

As 120 : 100 :: 32 : 26*66 „ „ sulphur. 

As 120 : 100 :: 64 : 53*33 „ „ oxygen. 



99*99 
Precisely the same method of calculation has been applied to the deter- 
mination of the percentages of hydrogen, sulphur, and oxygen. As the 
results seldom work out to a terminated decimal, the added percentages 
usually amount to only 99*99 ■ but by continuing the calculation any 
additional number of 9's could be obtained, and as 0*9 recurring is equal 
to 1*0, so 99*9 recurring is equivalent to 100*00. As another example, 
let it be required to determine the percentage of base and anhydrous 
acid respectively in calcium phosphate. This salt is represented by 

(Ca O \ P 2 5 

(40 + 16=)&Qx3 62 + 80 



168 + 142 = 310 

The molecule, which weighs 310, contains 168 of lime (CaO), and 142 
of phosphoric anhydride (P 2 5 ), consequently 

As 310 : 100 : : 168 : 54*19 per cent, of lime. 

As 310 : 100 :: 142 : 45*81 ,, „ phosphoric anhydride. 



100-00 

30. Formula from percentage Composition. — Let the fol- 
lowing represent the results of analysis of a body : — 
Sodium 16*79 per cent. 
Nitrogen 10*22 „ 

Hydrogen 3*65 „ 

Phosphorus 22*63 
Oxygen 46*71 „ 



100*00 

As a first step toward obtaining the formula, divide the percentage of 

each element by its atomic weight, the result will be a series of numbers 

in the ratio of the number of atoms of each element — 

16-79 
no = 0-73 of Sodium. 



INTRODUCTORY. 17 



10-22 

-|£- = 0.73 of Nitrogen. 

3.65 
=— = 3-65 „ Hydrogen. 

22-63 



31 
46-71 



= 0*73 ,, Phosphorus. 

= 2-92 „ Oxygen. 

It is next necessary to find the lowest series of whole numbers that 
correspond to these ; such a series may be obtained by dividing each 
number by the lowest one of the series — 

0-73 
0-73 
0-73 
0-73 

= o atoms ,, Hydrogen. 



= 1 atom of Sodium. 
= 1 ,, ,, Nitrogen. 



0-73 
0-73 



Tyjn = 1 atom „ Phosphorus. 
= 4 atoms ,, Oxygen. 



2-92 
MS 



The formula of the compound is, therefore, 2>TaNH 5 P0 4 ; its name is 
" hydrogen ammonium sodium phosphate." The formula obtained in this 
way is the simplest possible for the body in question : it is evident that 
the percentage composition would be the same if there were double or 
any other multiple of the number of atoms of each element in the mole- 
cule. Other considerations are taken into account in determining 
whether the correct molecular formula is really the simplest thus ob- 
tained, by calculation, from the percentage composition, or a multiple 
of the same. Such simplest possible formula is termed an Em- 
pirical Formula. 

31. Calculations Of Quantities. — An exceedingly common type 
of calculation is that in which it is required to know the quantities of 
one or more bodies required to produce a certain quantity of another 
body. Thus, hydrogen is commonly obtained by the action of zinc on 
sulphuric acid ; suppose that 10 grams of hydrogen are required for 
some operation : what weights respectively of zinc and sulphuric acid 
are necessary for the purpose % Here, again, the equation gives the 
relative weights of each element and compound participating in the 
reaction. In every such calculation it is absolutely necessary that the 
equation and combining weights be known ; but granted these, no other 
difficulties arise beyond those which can be readily overcome by an 
intelligent application of the principles of proportion. 

In the case in question the equation is : — 
c 



18 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



Zn 
65 


+ H 2 S 4 

2 + 32 + 64 


= Zn S 4 + 
65 + 32 + 64 


H 2 . 

2. 



98 161 

Zinc. Sulphuric Acid. Zinc Sulphate. Hydrogen. 

To produce two parts by weight of hydrogen, 65 of zinc and 98 of 
sulphuric acid are required, then — 

As 2 : 10 : : 65 : 325 grams of zinc required. 

As 2 : 10 : : 98 : 490 ,, sulphuric acid required. 

Another instance may be given, in which not only weights but also 
volumes of gases have to be calculated. It is required to know how 
much carbon dioxide gas in cubic centimetres and in cubic inches is 
evolved by the fermentation of 28*35 grams ( = 1 ounce) of pure cane 
sugar, the gas being measured at a temperature of 20° C. and 765 milli- 
metres pressure ; it being assumed that the whole of the sugar is re- 
solved into alcohol and carbon dioxide. The chemical changes involved 
in this process may be represented by the following equations — 

^12 H 22 ^11 + H 2 = 2 ^6 H 12 ( . 

H4 + 22 + 176 2 + 16 72 + 12 + 96 

342 18 2 x 180 = 360 

Cane Sugar. Water. Glucose. 

In the first place one molecule, equalling 342 parts by weight of cane 
sugar, is converted into two molecules of glucose each weighing 180, or 
the two weighing 360. 

2 C 6 H 12 G = 4 C 2 H 5 H O + 4 C 2 
72 + 12 + 96 24 + 5+1 + 16 12 + 32 

2 x 180 = 360. 4 x 46 = 184. 4x44 = 176. 

Glucose. Alcohol. Carbon dioxide. 

The two molecules of glucose, weighing 360, are next decomposed into 
four molecules of alcohol, having a total weight of 184 ; and four mole- 
cules of carbon dioxide each weighing 44, and the whole, 176. From 
342 parts by weight of cane sugar, 176 parts by weight of carbon di- 
oxide are produced ; then — 

As 342 : 28*35 : : 176 : 14-59 grams of carbon dioxide, yielded by 
28*35 grams of cane sugar. 

The next step is to determine what is the volume of 14*59 grams of 
carbon dioxide at N.T.P. The molecular weight of carbon dioxide 
being 44, its density must be 22 : one litre of hydrogen weighs 0*0896 
grams, and therefore 1 litre of carbon dioxide must weigh 0*0896 x 22 



1*9712 grams ; then 



14*59 

7*401 litres at N.T.P. 



1*9712 

Applying the laws previously given by which the relations between the 
volume and temperature and pressure of a gas are governed, then 
As 273 : 293 :: 7*4011 2 93 x 760 x 7*401 

765 : 760 J 273x765 

= 7*891 litres at 20° C. and 765 m.m. pressure = 7891 cubic centimetres. 






INTRODUCTORY. 19 



As 16-39 c.c. = 1 cubic inch, then 

7891 

lA no =481*7 cubic inches. 

28*35 grams or one ounce of cane sugar would yield, according to the 
question given, 7891 c.c. or 481*7 cubic inches of carbon dioxide gas at 
20° C. and 765 m.m. pressure. 

The weight of sugar necessary to yield a certain volume of gas would 
be calculated on the same principles ; as an illustration, the reverse of 
the calculation just made is appended. Require to know the weight of 
cane sugar necessary to produce 431*7 cubic inches or 7891 cubic inches 
of carbon dioxide gas at 20° C. and 765 m.m. pressure. 

~m^w^ =rm c - c - at N * T * P * = 7 - 401 litres * 

7*401 x 1*9742 = 14*59 grams of C0 2 . 
As 176 : 14*59 :: 342 : 28*35 grams of cane sugar required. 

32. Gaseous Diffusion. — It is a well-known fact that gases mix 
with each other with remarkable readiness. For instance, if in a large 
room a jar of chlorine is opened at the level of the floor, the presence of 
the gas may be detected by its powerful odour, within a few seconds, in 
every part of the room. The natural process by which the chlorine is 
thus disseminated through the air is termed "gaseous diffusion;" it 
takes place between gases, even though the heavier is at first at the 
lower level. In other words, a heavy gas will diffuse up into a super- 
incumbent light gas, while the light gas will make its way downwards 
and mix with the heavier one. In this way different gases, when 
placed in the same space, rapidly produce of themselves a uniform 
mixture. This process of diffusion will also go on through a porous 
membrane, as, for example, a thin diaphragm of plaster of Paris or 
porous earthenware. Thus, if a vessel be divided into two parts by 
a thin partition of porous material, and the one half be filled with one 
gas and the other with another, they will be found after some time to 
have become thoroughly intermixed with each other. The rate of 
diffusion of all gases through such a diaphragm is not the same, but 
depends on their densities. The rate of diffusion of gases is 
inversely as the square root of their density. Thus, hydrogen 
and oxygen have respectively densities of 1 and 1 6 ; hydrogen diffuses 
four times as rapidly 'as does oxygen. 

33. Osmose and Dialysis. — Liquids which are miscible with 
each other — (i.e., readily mix when placed together) — also undergo 
diffusion more or less rapidly. The laws governing diffusion of liquids 
are more complex than those affecting the diffusion of gases : not only 
gases, but also liquids, are capable of diffusion through a porous 
diaphragm; such diffusion is termed "Osmose." Some of the 
most remarkable and important phenomena of liquid-diffusion are those 
exhibited by aqueous solutions of different substances. Thus, let a sort 
of drum-head be made by stretching and fastening a piece of bullock's 
bladder, or either animal parchment or vegetable parchment paper, over 
a cylinder of some impervious material as glass or gutta-percha. Float 
this in a vessel of pure water, and pour inside it a strong solution of 



20 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

common salt. The brine and the pure water will only be separated from 
each other by the thin membrane of bladder or other similar material. 
After the lapse of some hours it will be found that the solution of salt 
will have diffused out through the membrane until the liquid both out- 
side and inside the floating vessel has the same strength. By repeatedly 
changing the water in the outer vessel, the whole of the salt might be 
removed from the solution within the cylinder. On the other hand, if 
a solution of gum were placed within the parchment drum, and sub- 
jected to precisely the same treatment, the gum would be found incap- 
able of diffusion through the membrane. If a mixture of brine and 
gum were placed in the cylinder with parchment bottom, and then 
floated on the surface of water, the salt would diffuse out and the gum. 
remain behind : in this manner a complete seperation of the two might 
be effected. The separation of bodies by their respective ability 
or inability, when dissolved, to diffuse through a porous mem- 
brane, is termed " Dialysis." 

34. Crystalloids and Colloids. — All bodies are capable of 

being divided into two great classes, known respectively as " crystalloids w 
and " colloids." Crystalloids are substances which, on changing 
from the liquid to the solid state, assume a crystalline form. 
Bodies are said to be crystalline when they consist of crystals, 
and for chemical purposes a crystal may be denned as matter 
which has spontaneously assumed during the act of solidifica- 
tion a definite geometric form. In crystals there is also a de- 
finite internal molecular arrangement related to the crystalline 
form by certain determinate laws. Solutions of crystalline bodies 
are usually, but not invariably, free from any marked viscosity. Crystal- 
line bodies are only soluble to a definite extent in water, the quantity 
dissolved depending more or less on the temperature : thus, 100 parts 
of water dissolve about 36 parts of salt. If more salt than this be added 
to water, it simply remains undissolved. Jelly-like substances as 
gum and gelatin are termed " Colloids," and do not acquire 
a crystalline form when assuming the solid state. The colloids 
form, when treated with water, sirupy, viscous, or jelly-like solutions. 
They may be said to be soluble in water in all proportions. Thus, if a few 
drops of water be added to a piece of dry gelatin, the water will be 
absorbed by the gelatin, and after a time will be uniformly diffused 
throughout the whole mass. Successive portions of water may thus be 
absorbed by the gelatin, which will become gradually softer, assuming 
the consistency of a jelly ; further addition of water produces a solution 
with more or less viscosity, depending on the degree of concentration. 
Crystalloids are especially susceptible of dialysis ; colloids 
exhibit under similar treatment very little tendency to pass 
through a porous membrane. The membranes used for dialysis 
consist of colloid substances : gelatin in the jelly-like form at times is a 
very convenient dialysing agent. The apparatus used for the purpose 
of effecting dialysing is termed a dialyser. The phenomena of liquid 
diffusion have an exceedingly important bearing on many chemical 
changes which occur during bread-making. 



i 




ELEMENTS AND INORGANIC COMPOUNDS. 21 



CHAPTER II. 

DESCRIPTION OF THE PRINCIPAL CHEMICAL ELEMENTS AND THEIR 
INORGANIC COMPOUNDS. 

35. Description of Elements and Compounds. — It is in- 
tended in this chapter to give a very brief description of those elements 
and their inorganic compounds, which are more or less directly connected 
with the chemistry of wheat, flour, and bread, and to which reference 
may be made in the latter part of this work. Such descriptions as are 
here given must not be viewed as being in any way a substitute for a 
careful study of elementary chemistry. It is thought, however, that to 
many readers, more particularly those who may not have the time for 
such a systematic course, an account such as is to follow will be found 
of service. 

36. Hydrogen, H 2 . — This element is a gas, and is the lightest 
substance known ; it is consequently selected as the standard by which 
the density of other gases is measured. One litre of hydrogen at N.T.P. 
weighs 0*0896 gram. Hydrogen has also the lowest atomic weight of 
all the elements, and is therefore also selected as the unit of the modern 
system of atomic or combining weights. Hydrogen is colourless, odour- 
less, tasteless, and non-poisonous. It is not capable of supporting 
respiration, and therefore animals placed therein quickly die through 
lack of proper air to breathe. Hydrogen is inflammable, and burns with 
a pale blue flame ; it does not support combustion. Hydrogen is only 
very slightly soluble in water. 

37. Oxygen, 2 - — This element is a colourless, odourless, and 
non-inflammable gas. Its most remarkable feature is that it supports 
combustion and also respiration. Bodies which burn in ordinary air 
do so because that substance is a mixture of oxygen and nitrogen ; they 
burn with much increased brilliancy in oxygen. The respiration or 
"breathing of animals consists of a removal of oxygen from the air, and 
a return thereto of carbon dioxide gas : the activity of oxygen renders it 
injurious to breathe in a pure state : in air, the nitrogen acts as a 
diluting agent, without modifying the essential characteristics of the 
gas. Oxygen is soluble in water to the extent of three volumes of the 
gas in one hundred volumes of water at 15° C. This quantity, though 
small, is of vast importance, as it thus supports the life of fishes, and 
has also a most important action on fermentation. Although oxygen is 
such an essential to most forms of life, there are some of the lower 
microscopic organisms towards which it acts as a most energetic poison. 
Compounds produced by the union of elements with oxygen are termed 
" oxides." 



22 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

38. Ozone, O s . — This body is a gaseous substance consisting of 
pure oxygen, but having a density of 24 instead of 16. This is due to 
there being 3 atoms of the element in the molecule, instead of 2 as in 
ordinary oxygen. Ozone has a peculiar odour ; and is produced during 
the working of a frictional electric machine, when its smell is recognised. 
Traces of this gas exist in the air in mountainous districts, and by the 
sea side. By exposure to a temperature of 237° C. ozone is transformed 
into ordinary oxygen. Ozone is a powerful oxidising agent, and is 
inimical to the growth and development of germ life. 

39. Water, H 2 0. — This most important compound consists of 
two volumes of hydrogen, united to one volume of oxygen, to form two 
volumes of water-gas or steam. By weight, water contains 16 parts of 
oxygen to 2 of hydrogen. Water in the pure state is odourless and 
tasteless ; viewed through thick layers it has a blue colour. At tem- 
perature below 0° C. water exists in the solid state ; on being heated, 
ice expands until a temperature of 0° C. is reached. At this point the 
ice begins to melt ; the temperature remains stationary until the whole 
of the ice is melted, but in order to effect the change from the solid to 
the liquid condition as much heat is required as would be sufficient to 
raise 79 times the weight of water from 0° to 1° C. Ice in melting 
contracts in bulk ; 10*9 volumes of ice producing 10 volumes of water. 
As the ice-cold water is further heated, contraction continues until a 
temperature of 4° C. is reached : at this point water is at its maximum 
density, and any given weight of it occupies its minimum volume. 
With further application of heat the water expands, and also rises 
steadily in temperature. In metal vessels open to the air, water boils 
at a temperature of 100° C. Continued heating now converts the whole 
of the water into steam, but does not raise the temperature. The 
quantity of heat necessary to convert the whole of the water at 100° C. 
into steam at the same temperature would raise 537*2 times the weight 
of water from 0° to 1° C. Steam in being further heated expands, and 
may have its temperature raised indefinitely : steam follows the same 
law of expansion, on increase of temperature, as do other gases. Steam, 
on being cooled, passes through a series of changes which are the 
exact converse of those just described. At all temperatures water gives 
off vapour, but with much greater rapidity as the temperature ap- 
proaches the boiling point. This vapour exerts a definite pressure, the 
pressure increasing steadily with the temperature ; at the boiling point, 
the pressure exerted by the vapour of water is exactly equal to that of 
the atmosphere : consequently, if the atmosphere pressure be diminished, 
the boiling point of water, and also that of all other liquids, is lowered. 
Advantage is taken of this property in many operations in the arts, thus 
in driving off the water from sugar solutions, the boiling is effected in a 
vacuum, and so the temperature prevented from rising to any great 
height. On the other hand, by subjecting water to pressure, its boiling 
point might be raised to any temperature attainable, the only limit 
being the capacity for resisting the pressure of the material of the vessel. 
The tubes of steam ovens are constructed on this principle — a certain 
quantity of water is sealed up in them, which, on being heated, is converted 
into steam, having a sufficently high temperature to effect the baking of 






ELEMENTS AND INORGANIC COMPOUNDS. 23 

bread. The boiling point of water also depends on any substances it 
may have in solution. Salt, and other non-volatile bodies, raise the 
temperature of the boiling point, but do not affect that of the steam 
produced, which immediately falls to 100° C. Admixture of volatile 
bodies lowers the boiling point ; thus water to which alcohol has been 
added boils at a temperature below 100° C. until the whole of the 
alcohol has been expelled. 

40. Solvent Power Of Water. — Water is, of all bodies, pre- 
eminently the solvent in nature. It dissolves more or less of all gases; 
thus, as previously stated, oxygen is soluble in it to the extent of about 
3 volumes per 100. On the other hand, one volume of water, at 0° C, 
dissolves 1050 volumes of ammonia gas. Many, if not most, liquids 
mix readily (or are miscible) with water in all proportions ; others, as oil, 
ether, &c, do not so mix, but are nevertheless frequently in part dis- 
solved by the water. Most solid bodies also dissolve in water ; water 
usually dissolves more of these substances when hot than when cold : 
this, however, does not invariably hold; thus, salt dissolves to as great 
an extent in cold as in hot water. As a result of this property, water 
is never found in a state of purity in nature. Even rain is found to 
have dissolved out traces of solid matter that were suspended in the 
air, while river and spring water is always more or less impure from 
saline and other matter dissolved from the soil and rocky strata from 
whence it is obtained. In addition to the solid matter there is also 
invariably more or less gas held in solution in natural waters. A 
further account of natural waters, having particular reference to their 
fitness for bread making, is given in chapter XVII. For chemical pur- 
poses all such water is purified by distillation, that is, it is converted 
into steam, and re-condensed ; the solid impurities then remain behind. 
This treatment does not, however, free the water from gases or from 
volatile impurities. For certain purposes where rigidly pure water is a 
necessity, special modes of preparation have to be adopted : these will 
be described in detail hereafter. 

41. Chlorine, 01 2 - — This element is, at ordinary temperatures, a 
gas of a greenish yellow colour, with a most pungent, acrid, and suffocat- 
ing odour and taste. The presence of comparatively small quantities 
renders air irrespirable. Chlorine is non-inflammable ; but, to a 
limited extent, supports combustion. Hydrogen burns in it readily, 
but carbon is incapable of direct combination with chlorine. Chlorine 
does not exist in the free state in nature ; it has so great an attraction 
for hydrogen that it slowly decomposes water, combining with the hy- 
drogen and liberating oxygen in the free state. Water dissolves 2-368 
volumes of chlorine at 15° C. : the solution has a powerful bleaching 
action on vegetable colours, and also is a most efficient disinfectant. 
Chlorine forms compounds with all other elements termed " Chlorides." 

42. Hydrochloric Acid, HC1. — This, the only known compound 
of hydrogen and chlorine, is a gaseous body. Hydrochloric acid gas is 
colourless, fumes in coming in contact with moist air, has a most pun- 
gent smell, and is neither inflammable nor a supporter of combustion. 
One volume of hydrogen unites with one volume of chlorine to produce 



24 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

two volumes of hydrochloric acid gas. The gas dissolves readily in 
water, one volume of which at 15° C. holds in solution 454 volumes of 
the gas. The concentrated solution fumes on exposure to air, and smells 
strongly of the gas ; it has an extremely sour taste, and turns litmus 
solution red. The commercial solution has a specific gravity of about 
1*16, and contains about 33 per cent, (one third) by weight of hydro- 
chloric acid. Hydrochloric acid attacks many of the metals, forming 
chlorides, with the evolution of hydrogen. Hydrochloric acid and the 
bases when placed in contact form the salts known as chlorides. Hydro- 
chloric acid and the chlorides may be recognised when in solution by 
their giving a curdy white precipitate on the addition of dilute nitric 
acid, and nitrate of silver solution. 

43. Chlorides. — Common salt, or sodium chloride, NaCI, is the 
most important of the chlorides. Its principal use is as an antiseptic 
or preventative of putrefaction ; its effect during fermentation of dough 
will be discussed hereafter. Other chlorides, as calcium chloride, CaCl 2 , 
will be referred to as occasion arises. 

44. Bleaching Powder, or Chloride of Lime, CaOCl 2 .— 

This body is produced by the union of lime, calcium oxide, with 
chlorine. The addition of almost any acid, even carbon dioxide, is 
sufficient to effect its decomposition, liberating free chlorine. Chloride 
of lime is consequently largely used for disinfecting purposes. 

45. Carbon, C. — This element is only known in the solid state, 
being incapable of liquefaction or vaporisation at the highest tempera- 
tures at our command. It exists in nature, uncombined with other 
elements, in two forms or varieties most strikingly different from each 
other. One of these constitutes the gem known as the diamond, the 
other is graphite, or black lead. Both these bodies are almost pure 
carbon. Carbon also occurs plentifully as a constituent of animal and 
vegetable substances, as flesh, bones, fat, wood, leaves, seeds, and the 
almost numberless bodies that may be obtained from them. Limestone, 
marble, and chalk rocks contain a large percentage of carbon ; so also 
does coal, which is simply fossilised wood. From flesh, bones, wood, 
and many other substances, carbon may be obtained by heating them 
to redness in a closed vessel : this form of carbon is termed " charcoal," 
that from bones being " animal," and that from wood " vegetable char- 
coal." Carbon prepared in this manner, or charcoal, is a black sub- 
stance. The operation of thus heating a substance in a closed vessel to 
a temperature sufficiently high to effect its dceomposition into volatile 
liquid and gaseous products, with usually, as in this case, a non-volatile 
residue, is termed " destructive distillation " All forms of carbon are 
inflammable. When burned with an insufficient supply of oxygen, 
carbon monoxide, CO, is produced ; with excess of oxygen, carbon 
dioxide, or C0 2 , is formed. Charcoal possesses a most remarkable pro- 
perty of absorbing and condensing gases within its pores ; thus, freshly- 
burnt wood charcoal is capable of absorbing about ninety times its 
volume of ammonia gas. Charcoal also absorbs considerable quantities 
of oxygen ; and among other gases those evolved during the putrefac- 
tion of animal and vegetable bodies. The gases resulting from put re- 



ELEMENTS AND INORGANIC COMPOUNDS. 25 

faction are largely composed of carbon and hydrogen, and when thus 
brought by their absorption within the charcoal so closely in contact 
with oxygen are rapidly burned or oxidised to carbon dioxide, water, 
and more or less of other inodorous and innocuous substances. Charcoal 
thus acts as a remedy for bad smells, and acts, not by masking them by 
a more powerful odour, but by absorption of the deleterious vapours 
and their conversion in harmless products. In this way, charcoal is also 
capable of removing evil smells from water : for instance, water from a 
stagnant pond, on being shaken up with charcoal, loses its disagreeable 
odour. Not only does charcoal act as an absorbent of gases, but it also 
removes many colouring matters from solution ; thus, a syrup of dark 
brown sugar, on being shaken up with animal charcoal and then fil- 
tered, may be made almost colourless. These properties of charcoal 
have led to its finding much favour as a filtering medium for the purifi- 
cation of water ; for this purpose it is, when fresh, of great efficacy, 
but after a time loses its activity by becoming saturated with the bodies 
it is intended to remove. All filters require from time to time to be 
taken apart, and the filtering medium removed and replaced by some 
fresh and pure material. Charcoal may be renovated by being heated 
to redness in a closed vessel. With these precautions, charcoal forms 
one of the best of filtering agents ; but without attention to continuous 
cleaning, filters, so far from purifying water, become positive sources of 
the most serious and dangerous impurities. Charcoal is frequently used 
in the laboratory for decolourising purposes. 

46. Carbon Monoxide, CO. — This compound is a colourless, 
odourless, and exceedingly poisonous gas. It is formed when carbon 
•dioxide gas passes over red-hot charcoal, as it frequently does, in a clean 
coke or charcoal fire. The carbon monoxide, thus produced, burns with 
a blue flame on the surface of the fire. The gas is inflammable, and in 
burning yields carbon dioxide. Carbon monoxide has no action on 
lime-water. 

47. Carbon Dioxide, C0 2 . — This gas plays a most important 
part in the chemistry of bread-making. It is colourless, has a sweetish 
taste, and peculiarly brisk and pungent odour. As carbon dioxide is an 
essential constituent of aerated waters, its taste and smell are familiar, 
being those perceived on opening and tasting the contents of a bottle of 
soda-water. Carbon dioxide is neither inflammable, nor under ordinary 
circumstances a supporter of combustion. The gas is poisonous to 
breathe, but may be taken into the stomach without injury. Liquids 
containing carbon dioxide gas in solution are marked by a pleasant 
brisk flavour. Carbon dioxide has a density of 22, and is 1-527 times 
as heavy as ordinary air. In the absence of air currents, it conse- 
quently has a tendency to remain a considerable time in a layer on the 
surface of liquids from which it is being evolved, particularly when they 
are in somewhat confined spaces. Carbon dioxide is soluble in about its 
own volume of water : as measured by volume the solubility is inde- 
pendent of the pressure to which the gas is subject. Thus, if 100 cubic 
inches of water be shaken up with carbon dioxide at the ordinary 
atmospheric pressure of about 15 lbs. to the square inch, the water dis- 



26 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

solves at 15° C. its own volume of the gas. If the pressure be increased 
to 30 lbs. per square inch, the water still dissolves 100 cubic inches of 
carbon dioxide, but as with double the pressure the density of the gas 
is doubled, it is evident that the doubled pressure results in effecting 
the solution of twice the weight of carbon dioxide gas. The weight of 
carbon dioxide dissolved by water is therefore in direct proportion to 
the pressure employed. Concentrated solutions of carbon dioxide gas 
in water are prepared by pumping the gas under pressure (some 10 or 
12 atmospheres) into a strong vessel, in which it is agitated with 
water. The solution thus obtained is permanent under pressure, but on 
its relaxation the carbon dioxide is again liberated in the gaseous state. 
Carbon dioxide may be obtained in a variety of ways ; the simplest is 
by the burning of carbon, or organic bodies containing carbon, in air or 
oxygen : — 

C + 2 C0 2 . 

Carbon. Oxygen. Carbon Dioxide. 

It is also produced when chalk, limestone, or marble (calcium carbonate) 
is heated to full redness — 

CaC0 3 = CaO. + C0 2 . 

Calcium Carbonate. Calcium Oxide (Lime). Carbon Dioxide. 

Likewise, by gently heating sodium bicarbonate or ammonium car- 
bonate — 

2NaHC0 3 = Na 2 C0 3 + H 2 + C0 2 . 

Sodium Bicarbonate. Sodium Carbonate. Water. Carbon Dioxide. 

(KH 4 ) 2 C0 3 = 2NH 3 + H 2 + C0 2 . 

Ammonium Carbonate. Ammonia. Water. Carbon Dioxide. 

Another method of obtaining carbon dioxide is by treating any car- 
bonate with an acid : the following equations represent a few of the 
principal of such reactions — 

CaCO s + 2HC1 = CaCl 2 + H 2 + C0 2 . 

Calcium Carbonate. Hydrochloric Acid. Calcium Chloride. Water. Carbon Dioxide. 

CaC0 3 + H 2 S0 4 = CaS0 4 + H 2 + C0 2 . 

Calcium Carbonate. Sulphuric Acid. Calcium Sulphate. Water. Carbon Dioxide. 

Na 2 C0 3 + 2HC1 -= 2NaCl + H 2 + C0 2 . 

Sodium Carbonate. Hydrochloric Acid. Sodium Chloride Water. Carbon Dioxide. 

(Common salt). 

Carbon dioxide is also evolved during alcoholic fermentation, and the 
putrefaction and decay of organic bodies. An aqueous solution of car- 
bon dioxide gas changes the colour of litmus solution from full blue to 
a port wine tint ; such a solution has feebly acid properties and forms 
with bases the salts termed carbonates. The solution in water may be 
viewed as carbonic acid, H 2 C0 3 ; hence the gas is frequently called 
carbonic anhydride. Formerly the term acid was applied, by some 
chemists, indifferently to the anhydrides and their compounds with 
water; carbon dioxide then received the name of " carbonic acid gas,' 7 
by which it is still popularly known. Modern definitions of an acid 
preclude this name being now correctly applied to what are properly 
termed anhydrides. 

48. Carbonates. — With the exception of those of the alkalies, all 
carbonates are insoluble in water; many are, however, dissolved by 
water containing carbon dioxide in solution. The most interesting ex- 



ELEMENTS AND INORGANIC COMPOUNDS. 27 

ample of this is the solution of considerable quantities of carbonate of 
lime in natural waters obtained from the chalk and other limestone- 
deposits. Such waters, although perfectly clear, become turbid on being 
boiled from fifteen to thirty minutes : the boiling drives off the carbon 
dioxide, and the calcium carbonate is precipitated in the insoluble state. 
The formation of carbonates is exemplified by the passage of carbon 
dioxide gas into lime water, i.e., a solution of lime in water, CaH 2 2 ; 
the insoluble calcium carbonate, or carbonate of lime, is produced, and 
turns the clear solution milky. This forms a useful and convenient 
test for the presence of carbon dioxide in any mixture of gases. Most 
carbonates are easily decomposed by the addition of an acid, with the 
formation of the corresponding salt of the acid used. Several instances 
of this action have been given when describing methods for the produc- 
tion of carbon dioxide. The acid, or bicarbonates, have one half only 
of the hydrogen replaced by a metal ; they may be produced by passing 
carbon dioxide gas to excess through a solution of the normal carbonates 
of the alkalies. The bicarbonates are readily decomposed by heat into 
normal carbonates, free carbon dioxide, and water. 

49. Compounds of Carbon with Hydrogen.— These are 

exceedingly numerous ; an account of some of those of most importance 
will be given when describing the organic bodies more particularly as- 
sociated with our subject. As a group, they are termed ''hydrides of 
carbon." 

50. Nitrogen, N 2 . — This gas constitutes about four-fifths, by 
volume, of the atmosphere ; it is also a constituent of nitric acid and its. 
salts, and of many animal and vegetable substances. Nitrogen is 
colourless, odourless, tasteless, non-infiammable, and a non- supporter of 
combustion. It does not readily enter into combination with other 
elements, and in the free state is marked rather by its neutral qualities 
than by any positive characteristics. In the uncombined state its prin- 
cipal function is that of a diluting agent in the atmosphere. Although 
not an active element, nitrogen forms an extensive series of compounds. 

51. The Atmosphere. — It has already been stated that the 
atmosphere consists essentially of oxygen and nitrogen ; these gases are 
not united in any way, but simply form a mechanical mixture. In 
addition to the nitrogen and oxygen, air contains small quantities of 
carbon dioxide, water vapour, and traces of other substances. Sub- 
joined is a table showing its average composition 

Oxygen, 2 , 

Nitrogen, N 2 , 

Carbon dioxide, C0 9 , 

Aqueous vapour, H 2 0, 

Nitric Acid, HN0 3 , ... 

Ammonia, NH 3 , ... ... .'-Traces. 

Hydrides of Carbon, ... ... J 

In /Sulphuretted hydrogen, SH 9 , \ 

towns. \ Sulphur dioxide, S0 2 , ... J " 

Air, freed from moisture and carbon dioxide, contains the following 
percentages of nitrogen and oxygen — 



20-61 

77-95 

0-04 

140 



28 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



By Measure. Bv Weight. 

Nitrogen, ... 79-19 76-99 

Oxygen, ... 20*81 23-01 



100.00 100.00 

In addition to the bodies already mentioned, air in most localities 
contains germs of microscopic organisms. 

52. Ammonia, N 3 H. — Traces of this gas, either in the free state 
or as salts, are found both in air and in water. Its great natural source 
is the decomposition of animal and vegetable substances which contain 
nitrogen as a constituent. In this way, ammonia is continually being 
formed in nature by the decay of refuse nitrogenous matter, such as the 
urine and excreta of animals, and other bodies. Many nitrogeneous 
vegetable and animal substances also evolve ammonia on being strongly 
heated : among these is coal, which thus forms the principal source from 
which ammonia is now derived. Ammonia is a colourless gas, with a 
most pungent and characteristic odour : in the concentrated state the 
gas acts as an irritant poison, but when diluted with air possesses a smell 
rather pleasant than otherwise. Ammonia does not support combustion, 
and at ordinary temperatures does not burn in air. The gas is very 
soluble in water ; the solution has the odour of the gas, and constitutes 
what is commonly known as " liquid ammonia," Ammonia acts as a 
powerful alkali, neutralising the strongest acids, and restoring the blue 
colour to reddened litmus. 

53. Ammonium Salts. — On the addition of an acid, such as 
either sulphuric or hydrochloric, to ammonia, the odour disappears, and 
the acid, as above stated, is found to be completely neutralised. The 
reaction may be expressed thus — 

M 3 + HC1 - NH 4 C1. 

Ammonia. Hydrochloric. Ammonium Chloride. 

2NH ? + H 2 S0 4 = (NH 4 ) 2 S0 4 . 

Ammonia. Sulphuric Acid. Ammonium Sulphate. 

On comparing, in each case, the formula of the resulting compound 
with that of the acid, it will be seen that the group NH 4 replaces the 
hydrogen of the acid. This compound, NH 4 , cannot exist in the free 
state, but occurs in a number of chemical compounds, and can be trans- 
ferred from one to another without undergoing decomposition. It is 
consequently viewed as a compound radical, and has received the name 
" Ammonium." The solution of ammonia in water may then be repre- 
sented as ammonium hydrate, NH 4 HO ; this body, which is alkaline to 
litmus, is then seen to be analogous to sodium hydrate, NaHO, the 
ammonium occupying a corresponding place to the sodium. This is 
seen the more clearly when a comparison is instituted between the 
action of the same acid upon each : — 

NH 4 HO + HC1 = NH 4 C1 + H 2 0. 

Ammonium Hydrate. Hydrochloric Acid. Ammonium Chloride. Water. 

NaHO + HC1 = NaCl + H 2 0. 

Sodium Hydrate. Hydrochloric Acid. Sodium Chloride. Water. 

Ammonium is often represented by the symbol " Am." instead of NH 4 . 



ELEMENTS AND INORGANIC COMPOUNDS. 29 



The stronger bases, as lime, CaO, or soda, NaHO, decompose ammonium 
salts with the liberation of ammonia : — 

NH 4 C1 + NaHO = NaCl + NH 3 + H 2 0. 

Ammonium Chloride. Sodium Hydrate. Sodium Chloride. Ammonia. Water. 

All ammonium salts volatise on being heated, leaving no residue, unless 
the acid be non-volatile, in which case the acid remains behind. 

54. Oxides and Acids of Nitrogen. — No less than five distinct 

compounds of nitrogen with oxygen are known. These, however, have 
but little connection with our present subject. Two of these oxides 
form acids with water — the acids being Nitric Acid, HN0 3 , and Nitrous 
Acid, HN0 2 . 

55. Nitric Acid, HN0 3 . — This is by far the most important oxy- 
compound of nitrogen. Its usual source in nature is the oxidation of 
animal matter in the soil. The nitric acid, thus produced, is found in 
combination with some base, usually as potassium or calcium nitrate. 
Pure nitric acid is a colourless fuming liquid ; commonly however 
the acid is of a slightly yellow tint, from the presence of some of the 
lower oxides of nitrogen. The pure acid has a specific gravity of 1-52, 
and mixes with water in all proportions. Nitric acid is a most power- 
ful oxidising agent, and attacks most animal and vegetable tissues with 
great vigour. It also freely dissolves most of the metals, forming 
nitrates. Gold and platinum are not affected by this acid when pure, 
but are dissolved with the formation of chlorides by a mixture of nitric 
with hydrochloric acid. Reducing agents convert nitric acid into 
nitrous acid, or some one or more of the oxides of nitrogen containing 
less oxygen. Under favourable circumstances, nitric acid may even be 
reduced to ammonia ; that is, the whole of its oxygen may be removed, 
and its place occupied by hydrogen. 

56. Nitrates. — The principal of these is potassium nitrate, KN0 3 , 
Like nitric acid, the nitrates are powerful oxidising agents. 

57. Nitrous Acid, HN0 2 , and Nitrites.— Nitrous acid is an 

unstable body ; it is at times found in water as an intermediate product 
in the oxidation to nitrates of nitrogeneous matter that may have been 
present. Potassium nitrite, KN0 2 , is one of its best known salts. 

58. Sulphur, S 2 - — This element is a brittle yellow solid, which 
burns in air or oxygen with the formation of sulphur dioxide, !S0 2 . 
The principal interest of sulphur, in connection with our present sub- 
ject, lies in its compounds. In addition to its occurence in many 
inorganic bodies, sulphur is one of the constituents of albumin and 
other animal and vegetable substances. 

59. Sulphuretted Hydrogen, SH 2 . — This body is a colourless 

gas, having a most disgusting odour, resembling that of rotten eggs; the 
gas is soluble in water, which at 15° C. dissolves 3 '23 volumes of sul- 
phuretted hydrogen. During the decomposition of substances, either of 
animal or vegetable origin, containing sulphur, sulphuretted hydrogen 
is one of the bodies evolved : it is from the presence of this gas that 
rotten eggs acquire their characteristic odour. Sulphuretted hydrogen 
is inflammable, and produces water and sulphur dioxide by its com- 
bustion. Moist sulphuretted hydrogen undergoes, in the presence of 



» 



30 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

oxygen, slow oxidation, with the formation of water and deposition of 
free sulphur: — 

2SH 2 + 2 = S 2 + 2H 2 0. 

Sulphuretted Oxygen. Sulphur. Water. 

hydrogen. 

60. Sulphur Dioxide, S0 2 - — This gas is produced by the com- 
bustion of sulphur in either air or oxygen : it is colourless, has a pun- 
gent odour, recognised as that of burning sulphur ; is neither inflam- 
mable nor a supporter of combustion. Sulphur dioxide is soluble in 
water, which at a temperature of 15° C. dissolves 47 volumes of the gas: 
the solution thus formed tastes and smells of the gas, it reddens and 
finally bleaches a solution of litmus. Sulphur dioxide is one of the 
most powerful antiseptics known. 

61. Sulphurous Acid, H 2 S0 3 , and the Sulphites. — Sul- 
phur dioxide, when dissolved in water, produces a somewhat unstable 
acid, H 2 S0 3 . The 'sulphites, or salts of this acid are mostly insoluble 
in water, the principal exceptions being sodium sulphite, Na 2 S0 3 , and 
potassium sulphite. In addition to the normal sulphites, acid or bisul- 
phites occur; these may be produced by passing excess of sulphur 
dioxide into a solution of the normal salt. The bisulphites readily 
evolve sulphur dioxide on being heated. Calcium sulphite is insoluble 
in water, but dissolves in a solution of sulphurous acid, forming calcium 
bisulphite, or as commonly called, " bisulphite of lime." Bisulphite of 
lime is largely used as an antiseptic. Under the influence of oxidising 
agents, sulphurous acid and the sulphites are oxidised to sulphuric acid 
and sulphates. 

62. Sulphuric Acid, H 2 S0 4 , and the Sulphates.— Sulphuric 

acid is one of the most useful chemical compounds known, forming 
as it does the starting point in the manufacture of a number of sub- 
stances of vast importance in the arts. When in the pure state, 
sulphuric acid is a colourless, odourless liquid of an oily consistency : 
this latter property has led to its receiving the popular name of " oil of 
vitriol ; " the acid, however, is in no way connected chemically with the 
olass of bodies known as fats or oils. Sulphuric acid is nearly twice as 
heavy as water, having a specific gravity of 1*842 ; it boils at a tem- 
perature of 338° C. Sulphuric acid has a great attraction for water, 
with which it probably combines to form definite hydrates ; considerable 
heat is evolved during the act of union. In consequence of this affinity 
for water, sulphuric acid is largely used as a desiccating or drying 
agent ; on exposure to the air the acid speedily increases in weight by 
absorption of water vapour, and the air becomes dry; hence, if a vessel 
of sulphuric acid be placed under a bell jar, it speedily produces a dry 
atmosphere inside. Less concentrated varieties of the acid form staple 
articles of commerce. Owing to this attraction for water, sulphuric acid 
is a most corrosive body ; wood, paper, and most vegetable and animal 
substances are vigorously attacked by it ; the acid combines with the 
hydrogen and oxygen of the substance in the proportions in which they 
form water, and leaves behind a mass of carbon, together with any 
excess of either hydrogen or oxygen that may have been present. 
This, of course, does not in all cases represent the whole of the chemical 



ELEMENTS AND INORGANIC COMPOUNDS. 31 



action that may have occurred. Dilute sulphuric acid contains water 
in excess, and therefore does not exhibit this dehydrating tendency 
when placed in contact with other bodies ; it is well to remember this, 
because in a number of reactions, where dilute sulphuric acid is em- 
ployed, it produces not merely less energetic action, but action absolutely 
opposite in character to that of the concentrated acid. The dilute acid, 
if allowed to evaporate in contact with paper, &c, acts in a similar 
manner to the strong acid, as the water dries off. Sulphuric acid forms 
a normal and an acid series of salts, of which Na 2 S0 4 , sodium sulphate, 
and NaHS0 4 . acid sodium sulphate, are, respectively, examples. Most 
of the sulphates are more or less soluble in water ; calcium sulphate is 
only slightly so ; barium sulphate is insoluble in water and dilute acids. 
Sulphuric acid and the sulphates may be detected in solution by the 
addition of hydrochloric acid and barium chloride, when they produce a 
white precipitate of BaS0 4 . 

63. Bromine, Br 2 ; Iodine, I 2 ; and Fluorine, P 2 .— These 

three elements are very closely allied in properties to chlorine ; they 
have no very intimate connection with the chemistry of wheat and flour. 
Bromine is a liquid ; iodine, at ordinary temperatures, is a solid body. 
Iodine is slightly soluble in water, readily soluble in alcohol or a solu- 
tion of potassium iodide, KI. Iodine, or its solution, produces a char- 
acteristic blue colour with starch : this reaction is of great delicacy, and 
is an exceedingly valuable test both for starch and iodine. Fluorine 
forms an acid with hydrogen, hydrofluoric acid, HF, which is charac- 
terised by its power of attacking and dissolving glass and the silicates 
generally. 

64. Silicon, Si ; Silica, Si0 2 ; and the Silicates.— Silicon is 

an element somewhat resembling carbon in some of its properties ; all 
that at present need be stated about it is, that it forms with oxygen an 
oxide, Si0 2 , analogous in composition to that of carbon, C0 2 . This 
oxide, Si0 2 , is termed silica, or at times, silicic anhydride. Flint and 
quartz are almost chemically pure forms of silica ; in this form silica is 
insoluble in water and all acids, and mixtures of acids, except hydro- 
fluoric acid. On being fused with an alkali, as KHO, or an alkaline 
carbonate, K 2 C0 3 , silica produces a glassy substance, entirely soluble in 
water : this body is potassium silicate, K 4 Si0 4 , and from it silicic acid, 
H 4 Si0 4 , may be obtained. Silicic acid is soluble in water, and is taste- 
less and odourless ; on being gently evaporated it first forms a jelly, 
and then, as the whole of the water is driven off, the silica remains as a 
white powder, once more insoluble in water and acids. As silica pro- 
duces a compound with water which, by action on bases, forms salts, 
silica is rightly viewed as an anhydride. The silicates are the principal 
constituents of the great rock masses of the earth and of soil. The 
natural silicates usually contain two or more of the following bases — 
iron oxides, alumina, lime, magnesia, potash, and soda. With the ex- 
ception of those of potash and soda, the silicates are mostly insoluble. 

65. Phosphorus, P 4 ; Phosphoric Acid, H 3 P0 4 ; and the 

Phosphates. — In properties, phosphorus is one of the most striking 
of the elements ; its attraction for oxygen is so great that it has to be 



32 CHEMISTRY OP WHEAT, PLOUR, AND , BREAD. 

kept under water in order to prevent its oxidation. Phosphorus occurs 
ordinarily as sticks of the colour and consistency of wax ; a piece or 
phosphorus appears luminous in the dark when exposed to air ; this is 
caused by its slow combustion. A slight elevation of temperature, or 
even friction, suffices to cause phosphorus to burn vigorously ; it then 
produces a vivid light, and forms, by union with oxygen, phosphorus 
pentoxide, P 2 5 , or, as it is sometimes termed, phosphoric anhydride. 
Phosphoric anhydride is a white powder, which combines with water 
with great avidity to form phosphoric acid, H 3 P0 4 . Phosphoric acid is 
principally of interest because of its salts, known as phosphates : of 
these the most important are calcium phosphate, Ca s (P0 4 ) 2 ; and potas- 
sium phosphate, K 3 P0 4 . Calcium phosphate is the principal constituent 
of the mineral matter of bones, and hence in some form or other is an 
absolutely essential article of food. Phosphates occur in some parts of 
all plants, and is derived by them from the soil. In wheat, the phos- 
phoric acid is mostly combined with potassium. The alkaline phos- 
phates are soluble in water ; the others are insoluble, but may be readily 
dissolved by the addition of nitric or hydrochloric acid. 

66. The Metals and their Compounds. — Within the limits 

of this work it would be impossible to give even the briefest systematic 
description of these bodies. An account follows of calcium and potas- 
sium, but such other metallic compounds as have any bearing on our 
subject will be described when reference to them is made. 

67. Calcium, Ca ; and its Compounds. — Calcium is scarcely 

known in the free state, as it has such an attraction for oxygen as to 
almost immediately, on exposure to the air, form calcium oxide. But 
one oxide of calcium is known that has any practical importance ; this 
body, CaO, is that commonly spoken of as " quicklime. " The salts of 
calcium are also commonly referred to as salts of lime ; this is not 
strictly correct, but in most cases makes no real difference. To this there 
is one exception, chloride of calcium, or calcium chloride, is CaCl 2 ; 
chloride of lime is a very different body, CaOCl 2 . Calcium oxide is a 
whitish grey substance, usually obtained by the action of heat on the 
carbonate; it is infusible at the highest temperatures at our command. 
Calcium oxide combines readily with water, with the evolution of consi- 
derable heat, forming slaked lime, or calcium hydrate, CaH 2 2 . Calcium 
hydrate occurs as a dry, white powder, which is soluble in water to 
the extent of one part in 600. This solution is that known as " lime- 
water," and is employed as a test for carbon dioxide. The solution of lime 
has a decidedly alkaline reaction, turning reddened litmus blue. Calcium 
produces an extensive series of salts ; of these calcium carbonate has 
been already referred to when describing carbon dioxide. The next most 
important salt is calcium sulphate ; this body is only slightly soluble, one 
part being dissolved by about 400 parts of water. The phosphate and 
chloride have already been referred to ; the latter has a great affinity for 
water, and consequently is often used as a drying agent ; it often can be 
used where sulphuric acid would be unsuitable from its other properties. 

68. Potassium, K; and its Compounds. — Potassium is a soft 

bluish white metal, winch has so great an attraction for oxygen that it 



ELEMENTS AND INORGANIC COMPOUNDS. 33 

has to be kept from contact with the air, and even liquids, as water, 
which contain oxygen as one of their compounds ; for this purpose the 
potassium is generally preserved in mineral naphtha, a compound of 
carbon and hydrogen. The normal oxide of potassium is K 2 ; this 
body has such affinity for water that it practically never occurs in the 
anhydrous state, but usually as the hydrate, KHO. Potassium hydrate 
is a white crystalline solid substance ; it melts at a red heat, and is 
supplied commercially either in sticks, or in lumps produced by breaking 
up fused slabs of the compound. Potassium hydrate is a powerfully 
caustic body, and rapidly destroys animal tissues. It is one of the most 
powerful alkalies known, restoring the colour to reddened litmus, and 
forming salts with acids. Potassium hydrate decomposes ammonium 
salts with the liberation of ammonia ; sodium hydrate and lime behave 
similarly in this respect. Potassium hydrate is very soluble in water ; 
the solution has a peculiar soapy feel to the fingers. Potassium hydrate 
has a great attraction for carbon dioxide ; its solution absorbs that gas 
with great rapidity, forming potassium carbonate, K 2 C0 3 . Potassium 
carbonate is a white deliquescent body (i.e., one that readily becomes 
moist through the absorption of water). Like other deliquescent bodies, 
potassium carbonate is very soluble in water ; the solution is strongly 
alkaline to litmus, although the salt is of normal constitution. In fact, 
the very strong bases, produce with certain weak acids, normal salts, in 
which the alkaline compound may be said to predominate. Potassium 
carbonate was at one time almost exclusively obtained from wood ashes. 
An acid potassium carbonate, KHC0 3 , also occurs ; this body is neutral 
to litmus, and is less soluble in water ; it is at a temperature of 80° C 
decomposed into the normal carbonate and free acid. 

69. Sodium. Compounds. — Sodium forms a series of compounds 
which closely resemble those of potassium ; of these the most familiar 
are sodium hydrate, NaHO ; sodium carbonate, Na 2 C0 3 ; acid sodium 
carbonate, NaHC0 3 ; and sodium chloride, NaCl. Sodium hydrate is 
a somewhat less powerful base than potassium hydrate. 



34 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



CHAPTER III. 

DESCRIPTION OF ORGANIC COMPOUNDS. 

70. " Organic " Chemical Compounds. — Chemical science is 

commonly divided into two branches, known respectively as "Inorganic" 
and " Organic " chemistry. Certain substances, whether they occur in 
nature or are prepared in the laboratory, are obtained from mineral 
sources : the bodies described in the preceding chapter are instances of 
such compounds. There are, on the other hand, bodies which are ob- 
tained either from the animal or vegetable kingdom. Animals and 
vegetables are organised bodies, that is, they have definite organs, which 
adapt them for that series of processes which constitutes what is called 
" life ; " hence chemical compounds having a vegetable or animal origin 
are termed " organic." Those which are not thus obtained from organic 
sources are termed " inorganic " compounds : the two names have also 
been given to the branches of chemistry which treat respectively of 
these two classes of bodies, and of their properties and reactions. It 
was formerly supposed that the so-called organic bodies could only be 
obtained from organic sources, but comparatively recent chemical in- 
vestigation has demonstrated that many such compounds can be 
produced by artificial means from the elements of which they are com- 
posed, without the intervention of living organisms, and even under 
such conditions as render the existence of living organisms an impossi- 
bility. Alcohol and its derivations are examples. The definition of an 
organic body as one produced as a result of "life" is evidently no longer 
tenable, and chemists have endeavoured, with more or less success, to 
frame new definitions of organic chemistry. As all organic com- 
pounds contain carbon, it has been proposed to define it as the 
" chemistry of the carbon compounds ; " again, as many organic bodies 
are well defined compound radicals, the phrase, " chemistry of the 
compound radicals " has been proposed. These definitions have not 
been found entirely satisfactory, as they are either too wide or too 
narrow. For our present purpose, Organic Chemistry may be viewed, 
with sufficient accuracy, as that branch of the science which 
treats of the composition and properties of those compounds 
whose usual source is either animal or vegetable. 

71. Organised Structures. — Although organic compounds can 
be prepared by artificial means, it must be clearly understood that no 
chemical processes have as yet been found capable of producing 
an organised structure ; further, all evidence hitherto obtained, so far 
as it goes, tends to prove the impossibility of such structures being 
formed other than through living agencies. For instance, starch is found, 



ORGANIC COMPOUNDS. 35 



when viewed under the microscope, to have a structural 
peculiar to itself. Starch may be dissolved, and after such solution 
again obtained in the solid state ; but the solid thus produced shows no 
traces of the original structure of the grains of starch ; neither is there 
known any artificial process by which the starch may again be built up 
into structures of the same kind as those in which it originally occurred. 
Similarly, it is impossible to artificially produce a blood corpuscle. The 
same law applies to minute organisms as yeast, bacteria, &c. ; none of 
these can be generated otherwise than through the agency of previously 
existing living beings of the same type. So far as any problem can be 
proved scientifically, this fact of the impossibility of spontaneous 
generation is abundantly demonstrated ; experimental evidence of 
a most conclusive character has shown as certainly as scientific research 
can, in any case, possibly show, that living organisms can only be formed 
by means of similar pre-existing organisms. Man may make a steam 
engine or a watch, but a yeast cell is beyond his power. 

72. Composition of Organic Bodies.— Organic compounds, 

generally, have a much more complicated chemical composition than 
have inorganic compounds ; they are mostly, however, restricted to 
•comparatively few elements. All organic bodies contain carbon ; many 
are composed of carbon and hydrogen only, a greater number consist of 
carbon, hydrogen, and oxygen ; while others contain the four elements, 
carbon, hydrogen, oxygen, and nitrogen. The majority of organic com- 
pounds belong to one or other of these series. Carbon, more than any 
other element, is remarkable for the property of, in compounds, com- 
bining directly with itself, and so forming most complicated bodies out 
•of comparatively few elements. 

73. Classification of Organic Compounds. — The number 

of these is so bewildering that, without some classification, it would be 
impossible to grasp their relationship to each other : recent chemical 
science has succeeded in very clearly demonstrating the constitution of 
a vast number of these bodies. There are, in the first place, large 
numbers of well defined compound radicals, consisting of carbon and 
hydrogen : it has been found possible to group these into distinct fami- 
lies, the members of each of which may be represented by a common 
formula. 

74. Organic Radicals. — The most important series of these is 
that known as the " Methyl," or " Ethyl " series ; these have the com- 
mon formula (C, l H 2u+1 ) 2 . This formula signifies that in the first place, 
the molecule consists of two semi-molecules that are similar in composi- 
tion ; secondly, that in each semi-molecule the number of atoms of 
hydrogen is one more than double the number of atoms of carbon. The 
following is a list of a few of the radicals of this series : — 



Methyl ... Me 2 ... |^ 3 



■m. i t?+ fC.H 5 /CH.> \ fCMeH, 

Eth ^ - Et * - ICA' or ( C 2 H 2 ) 2 ' or ICMeH; 

Propyl ... Pr 2 ... ggj, or {™* 



36 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 



Butyl ... Bu 2 ... jp 4 



.C4H9 

Amyl ... Ay 2 {£*| 

Caproyl ... Cp 



/C„H 13 
(C fi H 13 

Each semi-molecule of these radicals behaves in compounds as though 

it were an atom of a monad element ; the atomicity is shown by the 

following graphic formulae — 

H H H 

I I I 

H— C— H— C — C — 

I I I 

H H H 

Methyl. Ethyl. 

From these formulae it is seen that in each case there is one of the 
carbon bonds free ; in the free state two semi-molecules unite by these 
bonds to form the molecule. The graphic formulae also show how each 
of the higher radicals of the series may be viewed as compounds of the 
next lower radical with an additional CH 2 . The temperature of the 
boiling points of these bodies increases as the series is ascended. 

75. Hydrides of Organic Radicals (Paraffin Group). — 

These bodies are compounds of the radicals with hydrogen, those of the 
series already referred to have the general formula, C n H 2n+2 . Among 
them there is, as the lowest, methyl hydride (marsh gas), CH 3 H or 
CH 4 ; from this the series ascends regularly to C 16 H 34 . These com- 
pounds are distinguished by their not being readily attacked by the 
most powerful oxidising agents, they consequently have received the 
name of " paraffins " (from the Latin, parum a finis, having little 
affinity.) The lower members of the series are gases, the middle are 
liquids, and the higher members are solid at ordinary temperatures. 
The paraffins are produced by the destructive distillation of wood, coal, 
and many other organic substances, and also occur in rock-oils. Some 
varieties of American petroleum consist almost entirely of paraffins. 
In distilling the crude petroleum, it is found that the temperature of 
the vapour produced rises as the operation progresses. The more volatile 
portions distil off first ; the distillate may be collected in separate por- 
tions or fractions; the operation is then termed " fractional distillation."" 
The lighter or more volatile paraffins constitute what is known as light 
petroleum spirit ; this substance, when carefully freed from solid im- 
purities, is of great use as a solvent for fatty substances, both in the 
arts and chemical analysis. Good light petroleum spirit should distil 
entirely at a temperature of 70° C. Such spirit is a mixture of several 
of the lower paraffins. The petroleum of commerce consists of a some- 
what higher fraction, and mineral lubricating greases and " vaseline" of 
a yet less volatile portion. The least volatile portion of all constitutes, 
when pure, the hard white solid substance known as " solid paraffin," or 
paraffin "wax." 

76. The Alcohols. — These bodies are hydrates of the organic 



ORGANIC COMPOUNDS. 37 



radicals ; they possess basic properties, and enter into combination with 
acids to form organic salts. Thus ethyl alcohol, being C 2 H 5 HO, is 
converted by the action of hydrochloric acid into C 2 H 5 C1, ethyl chloride. 
This reaction is analagous to that by which sodium hydrate is converted 
into sodium chloride. Of the various alcohols, those of the methyl 
series are the most important, and are represented by the formula, 
C n H 2H+1 HO. Subjoined are a few examples of these compounds : — 

Methyl alcohol, CH 3 HO, or {^^ Butyl alcohol> c^HO. 

Ethyl „ ,C 2 H 5 HO,or{^3 H() ^ ^ , o^HOl 

Propyl „ ,C 3 H 7 HO. Melissic „ , C 30 H 60 HO. 

The lower members of the series are liquid, and the higher solid. 

77. Methyl Alcohol, CH 3 HO.— This body, in an impure form, is 
yielded on the destructive distillation of wood, and hence is commonly 
known as "wood spirit," or "wood naphtha." This crude preparation 
has a nauseous flavour which renders it unfit for drinking : the pure 
methyl alcohol has, on the contrary, a purely spirituous taste and odour. 
Methyl alcohol mixes in all proportions with water, ethyl alcohol, and 
ether ; it has at 15° C. a specific gravity of 0*8021. 

78. Ethyl Alcohol, {o^feo, or 2 H 5 HO.-This body con- 
stitutes the active ingredient of beer, wine, and of all spirituous liquors, 
as brandy, whisky, &c. The term " alcohol," when used without any 
prefix, is always understood to refer to this compound, which is known 
popularly as " spirits of wine." Alcohol may be produced artificially 
from its elements by purely chemical means, but is always manufactured 
by the process of fermentation, of which a detailed account is hereafter 
given. Pure ethyl alcohol is a colourless, mobile liquid, having an 
agreeable spirituous odour, and a burning taste. Alcohol is inflam- 
mable, and burns with a scarcely luminous smokeless flame, evolving 
considerable heat ; it is on this account largely used in " spirit " lamps 
as a fuel. Alcohol rapidly evaporates at ordinary temperatures, and 
when pure, boils at 78*4° C. ( = 173'1° F.) At a temperature of 
15 "5° C, alcohol has a specific gravity of 0*79350 ; that of water, at the 
same temperature, being taken as unity. Alcohol mixes with water, 
and also ether, in all proportions : for the former compound it has a 
great affinity, and evolves considerable heat on the two being mixed ; 
the volume of the mixture is less than that of the two liquids taken 
separately. As previously mentioned, alcohol is manufactured by fer- 
mentation • this process is only capable of producing a comparatively 
dilute solution of alcohol in water. In order to obtain a stronger spirit, 
the fermented liquid is distilled ; as alcohol boils at a lower temperature 
than water, the earlier portions of the distillate are the stronger in 
spirit, until finally no alcohol remains in the liquid being distilled. It 
is not possible to obtain in this manner alcohol free from water, as even 
the very first portions of spirit which distil over carry water with them. 
By several times distilling the spirit it is possible to obtain a mixture 
containing about 90 per cent, of the pure spirit : special distilling 



38 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

arrangements have resulted in the production of a distillate containing; 
as much as 95 per cent, of alcohol. In order to remove this small 
quantity of water, the spirit is treated with quicklime or potassium 
carbonate, and then allowed to stand, and after a time distilled : in this 
manner alcohol can be obtained in which there is only the most minute 
trace of water. This desiccated alcohol is termed " absolute " alcohol. 
Alcohol is of very great use as a solvent, particularly for many organic- 
bodies ; it also acts as an antiseptic, and hence is employed for the pre- 
servation of biological and other specimens. The solvent power of 
alcohol is modified considerably by its admixture with more or less 
water : for many purposes alcohol of a certain definite strength is neces- 
sary. As water and alcohol have different densities, and as density is 
easily measured, it is a usual method of testing the strength of alcohol 
to take its specific gravity. Tables have been prepared giving the 
strength in percentages of alcohol present for different densities. Three 
distinct standards of strength of alcoholic spirit are commercially recog- 
nised. The " Rectified Spirit of Wine " of the British Pharmacopoeia 
is the strongest spirit that can be produced by the ordinary methods of 
distillation : such spirit should contain 84 per cent, by weight of abso- 
lute alcohol, and should have a density of 0-838. " Proof Spirit " is a 
term that has survived its original application : it is now legally defined 
as spirit of such a strength, that 13 volumes of it shall weigh at 51° F_ 
the same as 1 2 volumes of water at the same temperature. Proof spirit 
has at 15-5° C. a density of 091984, and contains 49*24 per cent, by 
weight of alcohol and 50*76 of water. Weaker spirits are defined as 
being so many degrees " under proof" (U.P.), while stronger spirits are 
referred to as being so many degrees " over proof" (O.P.) A spirit of 
10 degrees U.P. is such that it contains 90 per cent, of proof spirit and 
10 per cent, of water; spirit of 10 degrees O.P. is of such a strength 
that it may be made up to 110 volumes by the addition of water, and 
would then have the same percentage of alcohol as proof spirit. Abso- 
lute alcohol is that, as before stated, which contains no water. For 
chemical purposes it is usual to specify the strength of alcohol, either as 
so much per cent, spirit, or by its density. When for any purpose it 
is directed that alcohol of a certain strength must be employed, parti- 
culars will be given as to its density ; for complete tables of densities 
and corresponding strengths, the larger treatises on chemistry must be 
consulted. 

79. Detection Of Alcohol. — Alcohol when present in any quan- 
tity is easily recognised by its smell ; in liquids which contain traces 
only, it is best to distil and then examine the first portions of the 
distillate. When using a Liebig's condenser, it will be seen, at the 
point where the vapour begins to condense, that when alcohol is present, 
the distillate trickles down the sides of the tube in peculiar oily looking- 
drops or " tears." This appearance ceases as soon as the whole of the 
alcohol has distilled off. Very minute quantities of alcohol suffice to 
produce this effect. Another and more delicate method for its detec- 
tion depends on the production of iodoform. This body has the symbol 
CHI 3 , and is similar in constitution to chloroform, CHC1 3 . The liquid 
under examination should first be distilled, and the tests applied to the 



ORGANIC COMPOUNDS. 39 



first portion of the distillate. Ten c.c. are to be taken and rendered 
alkaline by the addition of about a quarter of a c.c. (five or six drops) 
of a 10 per cent, solution of sodium hydrate; the liquid must next be 
warmed to about 50° C, and then a solution of potassium iodide, satu- 
rated with iodine, added drop by drop until a slight excess of free iodine 
is present ; this is indicated by the liquid acquiring a permanent sherry 
yellow tint. The liquid must next be just decolourised by the addition 
of a minute quantity of the sodium hydrate solution. If there be any 
alcohol present, a yellow crystalline precipitate of iodoform gradually 
forms. Certain other organic compounds, however, are capable of pro- 
ducing the same reaction. 

80. Methylated Spirits Of Wine.— Alcoholic liquors are sub- 
ject to a high duty ; consequently, for purposes other than the production 
of drinkable spirits, the Excise authorities permit the sale, duty free, of 
a mixture of nine volumes of rectified spirit, with one volume of com- 
mercial wood spirit. This mixture is known as " methylated spirits of 
wine ; " the impurities of the wood spirit impart a flavour which renders 
the whole absolutely undrinkable, except to the palates of the most 
debased dipsomaniacs. For most laboratory operations, methylated spirits 
can be used as a substitute for rectified spirits of wine : for delicate 
purposes it is well to re-distil the spirits prior to use. Methylated 
spirits may be rendered almost absolute by adding about one-third of 
its weight of recently burned quicklime, and thoroughly shaking : the 
mixture must be allowed to stand some three or four days, and the 
shaking repeated two or three times daily. The spirit must then be 
distilled, precautions being taken to prevent the temperature unduly 
rising. The still should be fixed in a water bath, consisting of an iron 
saucepan containing brine. The clear portion of the spirits should first 
be poured into the still, without disturbing the sediment, and distilled to 
dryness by application of heat to the water bath. Care must be taken 
that the bath does not boil dry. The pasty mass of lime may next be 
placed in the still, preferably in small quantities at a time, and heated 
by the bath so long as any alcohol distils over. An efficient condensing 
worm must be used, and the tube connecting it with the still ought to 
be a long one. At the close of the operation the lime may be removed 
from the vessel used as a still by soaking with water. 

81. Propyl, Butyl, and Amyl Alcohols. — These bodies are 

produced in small quantities during fermentation. They all boil at a 
higher temperature than ethyl alcohol, and are found in the residual 
liquor after most of the spirit has been distilled over. Propyl alcohol 
occurs in the residues of the distillation of the fermented liquor of the 
marc of grapes in the production of low-class brandy. Butyl alcohol 
occurs similarly as one of the bye-products in the preparation of spirits 
(rum) from the molasses of beet-root sugar. Amyl alcohol is the chief 
constituent of the analagous substance produced during the manufacture 
of alcohol from potatoes or grain. Amyl alcohol is an oily looking 
liquid, which does not mix with water, but with alcohol and ether in all 
proportions; it boils at 137° C. Amyl alcohol has a strong, disagree- 
able smell, and burning taste. Its intoxicating effects are similar to 



40 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

those of ethyl alcohol, but a few drops of amyl alcohol suffice to produce 
all symptoms of intoxication ; it has been estimated that amyl alcohol 
is fifteen times as intoxicating as is ethyl alcohol. More or less of this 
alcohol is found in newly made spirits, hence new whiskys, especially 
such as have been manufactured in " small" stills, are exceedingly de- 
leterious ; by keeping, the amyl alcohol is oxidised into harmless 
compounds. 

82. Fusel Or FoilSel Oil. — This name is applied to the oily mix- 
ture of spirits above referred to as being formed during fermentation. 
The fusel oil of potato and grain spirits principally consists of amyl 
alcohol. 

83. Glycerin, C 3 H 5 (HO) 3 . — In constitution this body is an alcohol. 
When pure, glycerin is a colourless, odourless, and thick sirupy liquid, 
having a sweet taste. Glycerin is one of the substances produced 
during the normal fermentation of sugar, and also is the basic con- 
stituent of fats and oils. 

84. The Ethers. — These bodies are the oxides of the organic 

[ p tr 

radicals ; the most important is ethylic ether, or ethyl oxide, < ~ 2 tt 5 0. 

When the term "ether" is employed without any qualification, it is this 
body to which reference is made. From its mode of preparation, ether 
is often termed " sulphuric ether ; " sulphuric acid, of course, does not 
enter into its composition. Ether is a colourless, very mobile liquid, 
having a peculiar, penetrating, and characteristic smell. This smell has 
given rise to the term " ethereal odour." Ether has a specific gravity 
of 0*736, it does not mix with water ; but, on being added, forms a 
layer on the surface. The ether dissolves a certain quantity of water, 
while the water, on the other hand, holds a portion of the ether in 
solution. Ether boils at 34*5° C, and is very volatile at ordinary 
temperature. The vapour is inflammable ; and, as may be gathered 
from the formula, is very heavy. Great care must be taken when 
working with ether to keep all lights at a safe distance. The high 
density of the vapour causes it to flow as a dense layer along a level 
surface for a considerable distance ; in this way, there is danger of the 
vapour communicating with a light that may be placed even at the 
further end of a long table. The rule should invariably be adopted of 
having no more of the liquid in the immediate neighbourhood, where ex- 
periments are being made, than is necessary for the purpose in hand ; 
the store bottle should not be kept in the laboratory. Ether is of great 
use as a solvent for fats, resins, and other organic bodies. 

85. Ethereal Salts. — These bodies are produced by the displace- 
ment of the hydrogen of acids by organic radicals ; the acid may be 
organic or inorganic. The compounds of such radicals, with chlorine, 
bromine, and iodine, are at times viewed as a sub-class of these bodies, 
and are termed " haloid " ethers. 

86. Chloroform, CHC1 3 . — In a number of organic compounds it is 
possible to replace the atoms of certain elements present by those of 
others ; in this way what are called " substitution products " are formed. 
Starting with methyl hydride, CH 4 , the hydrogen of this body may be 



ORGANIC COMPOUNDS. 41 



replaced atom by atom by chlorine until CC1 4 is formed The replace- 
ment of three atoms of hydrogen by chlorine results in the production 
of chloroform, CHC1 3 . This compound is at ordinary temperatures a 
heavy volatile liquid, having a specific gravity of 1 -48. The vapour of 
chloroform has a peculiar but pleasant smell, and when inhaled produces 
insensibility to pain, while in less quantities it causes stupefaction. 
No danger need, however, be apprehended during any ordinary working 
with this substance. Chloroform boils at a temperature of 60*8° C. 
Chloroform, like ether, acts as a solvent of many organic bodies ; it is 
not soluble in water, and after being shaken up with that liquid more 
or less quickly subsides and forms a layer at the bottom. 

87. Iodoform, CHI 3 . — This is a yellow solid body, analogous in 
-constitution to chloroform. 

88. Organic Acids. — These bodies constitute a numerous class 
of organic compounds ; like the radicals, they are capable of subdivision 
into distinct families, the members of which exhibit considerable re- 
semblance to each other. Several of these groups of acids are deriva- 
tives from corresponding series of alcohols. 

89. Fatty Acids, or Acids of Acetic Series.— These acids 

fC H 

may be represented by the general formula,-^ pfvxf q 1 ' The lowest mem- 

( TT 

her of the series is formic acid, < noTTO or HCH0 2 . The next and 

{CTT 
POTTO or -^^2^3^2- Acetic acid is the 

derivative from ethyl alcohol. It will be of service to place side by side 
for comparison the formulae of ethyl and some of its principal deriva- 
tives : — 

{ 

Ethyl. Ethyl Oxide or Ether. 



C 2 H 5 / C 2 H 5Q 

C 2 H 5 '• C 2 H 5 



O TT T-TO J 3 J 3 3 

Utt 5 ±iU, or | QgyrjQ J COH COHO 

Ethyl Hydrate or Alcohol. Acetic Aldehyde. Acetic Acid. 

J3y oxidising agents, two atoms of hydrogen may be removed from 
^alcohol with the formation of acetic aldehydride. This body is formed 
as an intermediate step between alcohol and acetic acid. Aldehyde 
readily combines with another atom of oxygen to form acetic acid. 
Aldehyde is one of the products of oxidation of casein, fibrin, and al- 
bumin. 

90. Acetic Acid is a liquid, which boils at a temperature of 117° 
•and freezes at 17° C. ; it has a sharp but pleasant smell, and is well 
known in a dilute form as vinegar. Vinegar is manufactured by a 
;species of fermentation from alcohol : its interest in connection with 
our present subject lies in the fact, that during many fermenting pro- 
cesses acetic acid is accidentally produced. 

91. Butyric Acid, {JjJoHO 0rH0 4H 7 O 2 . -This body bears the 
same relation to butyl alcohol that acetic acid does to that of ethyl. 



42 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

Butyric acid occurs in rancid butter, sweat, and many animal secretions. 
It is also one of the products of putrefaction, or putrid fermentation, of 
many organic substances ; for instance, it may be formed in consider- 
able quantity, by the action of putrid cheese on sugar. Butyric acid is- 
a liquid having a sharp odour resembling that of rancid butter. 

92. The Higher Fatty Acids. — These have received their 
special name because of their occurrence as constituents of many na- 
tural fats ; among those thus found are butyric acid (above described) , 

f O FT" [ f 1 FT 

palmitic acid, < pqttq or HC 16 H 3] 2 ; margaric acid, < noHO or 

HC l7 H 33 2 ; and stearic acid, i nr\jr 3 A or HC 1S H 35 2 . These latter 

bodies are at ordinary temperatures fatty solids, melting into oils with 
an increase of temperature. Physically, they bear little resemblance to 
acetic acid; but the formulae at once show their similarity in constitution. 

93. Fats and Soaps, or Salts of Higher Fatty Acids.— 

Most natural fats are salts of the higher fatty acids, with glycerin as 
the base ; for example, mutton fat is essentially composed of the 
stearate of glycerin. This body may be artificially produced by heating 
together stearic acid and glycerin, according to the following equation — 

3HC 18 H 35 2 + C 3 H 6 (HO) 3 = C 3 H 6 (C 18 H 35 5 ) 3 + 3H 2 0. 

Stearic Acid. Glycerin. Glycerin Stearate. Water. 

Some natural fats contain an excess of the fatty acid over and above- 
that sufficient to combine with the whole of the glycerin present. 

In addition to the " fatty " acids, acids of another group, known as- 
the oleic series, are found as constituents of natural oils and fats. Oleic 
acid, HC 18 H 33 2 , is the product of oxidation of an alcohol of the family 
C n H 9n _ 1 H0 series : it will be noticed that the formula of the acid 
differs from that of stearic acid by containing two atoms less of hydro- 
gen : this difference follows from the difference in the typical formulae 
of the two series of alcohols. The oleates of glycerin constitute the oils. 
or liquid portions of fats. 

By the action of alkalies, as soda or potash, the fats are decom- 
posed, with the formation of sodium or potassium salts of the fatty acids, 
and the liberation of glycerin in the free state. These salts constitute 
the bodies known technically as "soaps," those of sodium are the 
"hard," and those of potassium "soft" soaps. The separation of fats 
into glycerin and the fatty acids may also be effected by forcing a 
current of steam through the melted fat. The glycerin distils over with 
the steam. This operation of decomposing fat, by the aid of alkalies, 
is termed " saponification," and in addition to its great use in the com- 
mercial manufacture of soap, constitutes a valuable method of investi- 
gating the composition and properties of natural fats and oils. 

Some few other organic acids of interest yet remain to be described,. 



among these there is- 



94. Lactic Acid, H0 3 H 5 O 3 . — This body occurs in sour milk, and 
is also produced in greater or less quantities during fermentation with 
ordinary commercial yeast. Lactic acid is a sirupy liquid of specific 



ORGANIC COMPOUNDS. 43 



gravity, 1-215, colourless and odourless, and having a very sharp sour 
taste. It forms a well-defined series of salts. 

95. Succinic Acid, H 2 4 H 4 O 4 . - Succinic acid is a white solid 
body, soluble in water. It is one of the bodies produced during the' 
normal alcoholic fermentation of sugar. On being heated, succinic acid 
evolves dense suffocating fumes. 

96. Tartaric Acid, H 2 C 4 H 4 O g . — This body Occurs naturally as a 
constituent of the juice of the grape, and in various other plants. It 
is when pure a white solid crystalline body, soluble in water, and 
possessing a pleasant sour taste. On being heated, tartaric acid evolves 
an odour of burnt sugar. Tartaric acid is dibasic, and forms both an 
acid and a normal series of salts, termed " tartrates." The well-known 
substance "cream of tartar" is acid potassium tartrate, KHC 4 H 4 6 ; this 
body has an acid reaction, and like tartaric acid, decomposes sodium 
carbonate with the evolution of carbon dioxide gas. As, however, one- 
half the hydrogen has been already replaced in cream of tartar by 
potassium, that salt has only half the power of decomposing sodium 
carbonate that is possessed by free tartaric acid. When acid potassium 
tartrate is neutralised by the addition of sodium carbonate, so long as- 
effervescence occurs, there is produced a double tartrate of potassium 
and sodium, KNaC 4 H 4 6 . This body is soluble in water, and is known 
as " Rochelle Salt." 

97 Definition Of Homologues, &C — At this stage of the sub- 
ject it will be convenient to explain the meaning which is attached to- 
" homologue " and other similar terms used in describing organic bodies. 
Series of bodies are termed homologous, in which their general 
constitution may be represented by a typical formula ; thus, the 
organic radicals of the methyl series are homologous, so too are the 
corresponding alcohols, and also the fatty acids. The melting and boil- 
ing points of the members of a homologous series usually rise as the 
series is ascended. When capable of being vaporised, their density in 
the gaseous condition increases with the ascent of the series. Usually, 
the lower members of a series of homologues are more chemically active 
than are those of a more complicated constitution. Many organic bodies 
are known which not only contain the same elements, but also contain 
them in the same proportion, while their physical and chemical char- 
acter show them, nevertheless, to be distinct compounds. Distinct 
compounds, having the same percentage composition, are said 
to be "isomers," or "isomeric" with each other. Isomerism may 
be of different kinds. Thus, bodies may have the same percentage 
composition, and yet have different molecular weights : in these cases 
the molecular weights are multiples of the simplest possible molecular 
weight that can be deduced from the percentage composition. Bodies 
having the same percentage composition, but different mole- 
cular weights, are said to be "polymers," or "polymeric" with 
each other. The following are instances of polymeric bodies : — 

Ethylene — C 2 H 4 . 

Propylene — C 3 H 6 . 

Butylene — C 4 H S . 



44 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

In addition to isomerism of the above type there is yet another more 
striking variety. When distinct chemical compounds have not 
only the same percentage composition, but also the same 
molecular weight, they are said to be " metamers," or " meta- 
meric " with each other. As examples of metameric compounds the 
following three bodies maybe cited — propylamine, methylethylamine, and 
trimethylamine. These three bodies all have the formula, NC 3 H 9 . That 
they are distinct compounds containing the same proportions of carbon 
and hydrogen, but united together to form different organic radicals, is 
seen when the formulae are written as below : — 

(C 3 H 7 fCH 3 fCH 3 

NlH N4C 9 H 5 NJCH 8 

(H |tf [CH 3 

Propylamine. Methylethylamine. Trimethylamine. 

The nature and constitution of these bodies are described in para- 
graph 99. 

98. Nitrogenous Organic Bodies.— Many organic compounds, 

both from animal and vegetable sources, contain nitrogen as one of 
their constituents. Of the great majority of these bodies nothing very 
definite is known as to their constitution ; a large number of them are 
basic in their character, and hence are known as nitrogenous organic 
bases, or "alkaloids." 

99. Substitution, or Compound, Ammonias. — Many of the 

nitrogenous organic bodies are built upon the same type as ammonia, 
and may be viewed as ammonia in which one or more of the atoms of 
hydrogen are replaced by compound radicals. These compounds are 
termed " amines," or " substitution ammonias." The three bodies, 
propylamine, methylethylamine, and trimethylamine, whose formulae are 
given in a preceding paragraph, are examples of amines. The methyl- 
amines are gases at ordinary temperatures, having a strong ammonical 
and fish-like smell. 

100. Alkaloids. — This name is applied to a class of organic bodies, 
most of which contain nitrogen, carbon, hydrogen, and oxygen. All 
these bodies are basic, while many are able to neutralise even the 
strongest acids, as sulphuric acid. They are, as a class, remarkably 
energetic in their action on animals ; thus, quinine and morphine are 
most powerful medicines, while strychnine and brucine are among the 
most violent poisons ; but little is understood of the constitution of the 
alkaloids ; it is probable that they are of the same type as the compound 
ammonias. For the sake of uniformity in chemical nomenclature, it has 
been proposed to restrict the termination " ine " to the alkaloids ; for 
this reason, glycerin, dextrin, &c, should never be written glycerine, 
dextrine, &c. 

101. Pepsin and Peptones. — Pepsin is a substance which con- 
stitutes the active digestive principle of the fluids of the stomach 
(gastric juice). Pepsin is soluble in water, but insoluble in alcohol or 
ether. A slightly acidulated aqueous solution of pepsin, especially at 
the temperature of the body, rapidly dissolves insoluble albuminous 
substances, as the white of hard boiled eggs or lean beef. The solutions, 



ORGANIC COMPOUNDS. 45 



thus obtained, do not coagulate on the application of heat, and contain 
the substance known as "peptone." The energy of pepsin is destroyed 
by boiling ; so also its digestive action is impeded by the presence of 
peptones themselves in excess. Consequently, when pepsin acts on 
albumin, &c, the action is at last arrested by the peptones produced. 
Dried pepsin, mixed with from 20 to 50 per cent, of starch, may now be 
procured as an article of commerce, being found of considerable value as 
a medicine. Pepsin Porci (i.e., that of the pig) is the variety most 
generally employed. There are several modifications of peptone, hence 
the common use of the plural, " peptones." These compounds do not 
differ very greatly in percentage composition from albuminous bodies ; 
they may be regarded as the product of one step toward their digestion. 
Subjoined are given the results of analyses of white of egg, and the 



b obtained thei 


■eirom : — 






White of Egg. 


Peptone. 


Carbon, 








5137 


50-87 


Hydrogen, 








7-13 


7-03 


Nitrogen, 








16-00 


16-34 


Sulphur, . . . 








2-12 


1-64 


Oxygen (with 


traces of 


phosphorus), 


23-38 


24-12 



100-00 100-00 



46 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



CHAPTER IV. 



THE MICROSCOPE, AND POLARISATION OF LIGHT. 



102. Object Of Microscope.— A description of the microscope, 
and method of using it, is given at this early stage, because the student 
will continually find it requisite to have recourse to this instrument 
from time to time, while going on with his study of the chemical proper- 
ties of the various grain constituents. In order to thoroughly under- 
stand the physical construction of bodies it is necessary to see them. 
The microscope is an instrument to enable us to see points of physical 
•construction which are so minute as to escape the unaided vision. 




FIG. 2.— THE MICROSCOPE. 



for good mi- 



103. Description of Microscope. — The demand 

•croscopes has led to the supply by a number of makers, both English 
and Continental, of really excellent instruments at low cost. In con 



THE MICROSCOPE. 47 



sequence, the microscope is not now, even to the general public, an un- 
familiar piece of apparatus. These pages are not the place where an 
exhaustive description of microscopes could with fitness be given, but as 
the instrument should be in the hands of every miller and baker, a few 
hints as to how to use it for such purposes as those occurring during 
milling and bread making will naturally find a place in this work. As 
an instrument suitable for the work of miller and baker, the writer has 
figured one supplied by Swift, of 81 Tottenham Court Road, London. 
These microscopes are cheap (in the best sense of the term), of excellent 
make, and always trustworthy. 

Every reader will probably be familiar with the general appearance 
■of the instrument as shown in the illustration. The microscope proper 
■consists of the stand, to which is attached the main tube of the instru- 
ment, by means of a sliding " dove-tail " arrangement, that can be 
raised or lowered by a rack and pinion : the pair of milled heads actuate 
this pinion. The stage, which has in this particular instrument a glass 
surface, is provided with a pair of springs for the purpose of holding 
-the object firmly while being examined. Underneath the stage is a 
plate or diaphragm, which can be rotated, and which contains a series 
of apertures of different diameters. Beneath this again is a concave 
glass mirror, so mounted as to be easily placed in any required position. 
The tube of the microscope, together with the stage and mirror, can be 
turned at any angle to the tripod stand, from the vertical to the hori- 
zontal. Within the main tube is fitted a second, known as the " draw 
tube," which can be pulled out if required, thus increasing the distance 
between the eye-piece and object glass. The lower end of this main 
tube is provided with an internal screw for the purpose of receiving the 
combinations of lenses known as " object glasses," or " objectives." The 
objectives of all the best makers are now cut with the same screw 
thread, and so are interchangeable. The "eye piece," also a lens com- 
bination, slides into the top of the draw tube. The objectives are named 
according to their focal length, and are consequently termed " 1-in. ob- 
jectives," tfcc. The greater the focal length the less is the magnifying 
power of an objective. The eye-pieces also vary in magnifying power, 
and are usually referred to as "A,""B" eye-pieces, and so on; the 
magnification increases with each successive letter of the alphabet, com- 
mencing with A. The student will require a series of these objectives, 
consisting of the 3-inch, 1-inch, and -J-inch ; these will be found to 
answer most purposes. For ordinary work the A eye-piece is sufficient, 
but a C eye-piece is also at times useful. The following accessories are 
requisite : one or two dozen glass slides, 3 inches by 1 ; some thin glass 
covers, these may be round or square, and should be about | inch dia- 
meter, or square ; a pair of fine forceps ; one or two needles set in 
handles ; a glass rod drawn out to a point at one end, and a small piece 
of glass tubing. All these may be obtained from the maker of the 
microscope, and are usually supplied in the case with the instrument. 
Other useful pieces of additional apparatus will be mentioned as neces- 
sity arises for their employment. 

A word may be said in the first place about the preserving of the 
instrument from injury. When not in use it should either be kept in 



48 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

its case, or what is more convenient, under a glass shade, as then it can 
be readily used when required. A mounted longitudinal section of a. 
grain of wheat should be purchased at the same time as the instrument; 
this is a very useful slide to possess, and will give the student an oppor- 
tunity of learning how to use his microscope before he proceeds to 
mounting objects for himself. 

104. HOW to use the Microscope.— To commence using the 
instrument, remove it from the case, take the 3-inch objective out of its 
box and screw it into the bottom of the tube ; next insert the eye-piece 
in its place. The lenses, if dusty, may be very gently wiped with either 
an old silk handkerchief that has been often washed, or a piece of wash- 
leather. One or other of these should be kept solely for this purpose. 
The less, however, that the lenses require wiping the better, as being 
made of soft glass, they easily scratch. When working on yeast, tem- 
porarily mounted in water or other liquid substance, it is necessary to 
set the stage horizontal, as otherwise the liquid flows downward. But 
with fixed and permanent objects the microscope should be inclined to 
an angle of about 45 degrees, as in such a position the eye is much less- 
fatigued during observation. The next requisite is light. In the day- 
time choose a room that is well lighted, if possible not by direct sun- 
light, but by a bright cloud. At night an argand gas lamp, especially 
if enclosed in a ground glass globe, makes a good source of light. Raise 
the microscope tube by turning the pinion until the end of the objective 
is about 3 inches from the stage. Place the mounted wheat-grain slide 
on the stage, and arrange the clips to hold it firmly. Next turn the 
mirror so as to throw the spot of light on the object. Now look down 
the eye-piece and lower the microscope tube until the object is focussed;, 
that is, until its outlines are seen clearly without being blurred. A 
word may here be said about the amount of light advisable ; generally 
speaking the rule may be laid down that it is wise to work with no 
more light than necessary. The light should not be bright enough to 
dazzle the eye in the slighest degree ; on the other hand, it should be 
sufficient for the object to be seen comfortably. The 3-inch objective 
will show the grain of wheat occupying almost the whole of the field of 
vision. Any object when seen through the microscope is inverted ; that 
is, the top is seen at the bottom, and the left side at the right. By 
pulling out the draw tube the object is still further magnified. 

In the next place, unscrew the 3-inch and substitute for it the 1-inch 
objective. The microscope tube will now have to be lowered con- 
siderably, until the object is again in focus. A portion only of the 
wheat-grain is seen in the field, but that portion is magnified to a much 
greater degree. 

The illumination is much less than with the 3-inch object glass, 
Notice that more of the details of the object can be distinguished. 

The -J-inch objective may now be tried. Unless the section is a very 
thin one, it will not, however, show up well. Having exchanged the 
inch for this power, lower the microscope tube until the end of the object 
glass is within an eighth of an inch from the slide ; then move the 
milled head very slowly and carefully, watching all the time until the 
object is again in focus : for this purpose it is well to move the slide 



THE MICROSCOPE. 49 



until a portion of the skin of the grain is in view. The milled head, 
shown just underneath the two connected with the pinion, may now be 
used for making the final adjustment of the focus. This latter milled 
head is termed the "fine adjustment," while that by means of the rack 
and pinion is spoken of as the " course adjustment." For the lower 
powers the course adjustment is sufficient. 

This exercise with the three powers will have shown the student the 
mode of using his microscope. He must accustom himself to moving 
the object about on the stage, so as to get any portion he wishes in 
view ; this presents some little difficulty at first, because the movement 
must be made in the opposite direction to that in which it is desired 
that the magnified image shall travel. 

105. Measurement of Microscopic Objects. — The micro- 
scope is not merely used for the purpose of seeing small objects, but, 
with the addition of certain accessories, is also employed for measuring 
their size. The first object requisite for this purpose is a " stage 
micrometer ; " an eye-piece micrometer should also be procured. The 
stage micrometer may consist of a fraction of an inch further divided up 
into tenths and hundredths, or preferably of a millimetre similarly 
graduated. The scale for this purpose is accurately photographed on a 
glass slip, the same as an ordinary slide. It will be remembered that 
the millimetre is very nearly the twenty-fifth part of an inch, conse- 
quently the tenth and hundredth of a millimetre may be taken as equal 
to the two hundred and fiftieth, and two thousand five hundredth part 
of an inch. Working with low powers, it is sufficient for rough 
purposes to place the stage micrometer face downwards on the object to 
be measured, and then to read the number of divisions of the micro- 
meter over which the object to be measured extends. This can only be 
done with powers sufficiently low to permit the lines on the micrometer, 
and the object under examination, to be in focus, or nearly so, at the 
same time. The eye-piece micrometer is, for all purposes, far preferable. 
This instrument consists of a scale, which may be an arbitrary one, 
fixed in the eye-piece. With the eye-piece in position, on looking down 
the microscope, both the eye-piece scale and the object are seen in focus 
together. The scale looks as though it were simply superposed on the 
object. The value of this scale varies with each different power 
employed, but may be determined in the following manner — screw the 
lowest power into the microscope ; put the stage micrometer on the 
stage, and read off carefully in tenths and hundredths of a millimetre 
the value of one division of the eye-piece micrometer. Next repeat the 
same measurement in exactly the same way with each of the other 
objectives. In these determinations the draw tube must invariably be 
in the same position ; it is best to have it always closed when the micro- 
scope is being used for measuring purposes. Thus, for example, with 
one of the microscopes in the possession of the writer, one division of the 
eye-piece with the lowest power is equal to 0*016 m.m. ( = 0*00064 
inch), the next 0-0064, the next 0*0038, and the highest power 0*0016 
m.m. Supposing that an object, under examination with the highest 
power, on being measured is 3*2 eye-piece divisions in length, then its 
real length is 0*0016 x 3*2 = 0*00602 m.m., or 0*0002 = T oVo of an inch - 

E 



50 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

106. The Micromillimetre. — When the dimensions of minute 
objects are expressed, either in inches or in millimetres, they require such 
a number of figures that it is difficult to at first realise the value of the 
dimension. It has therefore been proposed to employ the one- 
thousandth part of a millimetre as a unit of length for microscopic 
measurements. This unit is called a micromillimetre, for which the 
following abbreviation, " mkm.,"may be used. The mkm. is also some- 
times called a " ju, " (pronounced mu) ; its value in inches is very nearly 
2"5Toi5" mcn - The eye-piece measurements referred to in the preceding- 
paragraph would have in mkms. the following values : — 

0-016 m.m. = 16'0 mkms. 

0*0064 m.m. = 6*4 mkms. 

0-0038 m.m. = 3'8 mkms. 

0*0016 m.m. = 1.6 mkms. 

107. Magnification in Diameters. — There remains to be ex- 
plained a convenient method of measuring the magnifying power of 
objectives and eye-pieces. A common method of expressing the value 
of particular combinations of these two is to say that they magnify so 
many diameters. A moment's reflection will show that the image seen 
with a microscope will vary in actual dimensions, according to whether 
it be supposed to be near to or far from the eye. The only real measure- 
ment, in fact, is the visual angle it subtends. This being the case, the 
measurement in diameters is always expressed with the understanding 
that the object is supposed to be 10 inches from the eye. 

Here for a moment a slight digression must be made. Most be- 
ginners when looking through a microscope close the eye not in use. 
This is a bad plan, as the eyes are thereby much more fatigued. Both 
eyes should be kept open. At first the surrounding objects are con- 
tinually being seen with the unoccupied eye, and it is apparently a 
hopeless case to see the object under the microscope at all. Practice 
overcomes this, but the writer has found the best plan is to fix to the 
microscope tube a piece of dead black cardboard, so that the unoccupied 
eye sees only a black surface. The object will now be observed with 
the greatest readiness, and probably not one quarter the fatigue. In a 
very short time the cardboard shield may be dispensed with, and the 
trained eyes so behave that the one is transmitting the view of the 
microscopic object to the brain, while the other is remaining idle and 
resting. The student should accustom himself to use either eye in- 
differently ; he will soon find that he will no more think of closing one 
eye when looking through his microscope than he would of tying his left 
hand behind his back before he shakes hands with his right 

Now, the object of our momentary departure will be evident ; the 
idle eye can, at will, be used for looking at something else, so that the 
one eye is looking at the microscopic object, the other, if wished, at say 
a piece of paper. Place the stage micrometer in focus, and fix a piece 
of stiff paper or cardboard as near as possible to the microscope, at 
right angles to its axis, and ten inches from the eye-piece. Look down 
the tube with the one eye, and with the other at the piece of paper. 
The magnified micrometer scale appears as though drawn on the paper. 



THE MICROSCOPE. 51 



Still using both eyes, trace with a pencil on the paper the exact position 
of each line representing the tenths or hundredths of the millimetre. 
Next measure on the paper the distance between the two marks traced 
from, say, the tenths of a millimetre ; suppose that this distance is five 
millimetres, then that particular combination of eye-piece and objective 
has a magnifying power of fifty diameters. Measure each other com- 
bination possible with the various eye-pieces and objectives in your 
possession in the same way. 

108. Microscopic Sketching and Tracing. — The above 

method of measuring is very useful, because with small objects occupy- 
ing a portion only of the field, it is possible to trace them on the paper 
in the manner described, and such tracings are then known to be 
magnified to the extent ascertained by previous measurement as directed. 
Such sketching by actual tracing is very desirable in microscopic work, 
as otherwise the student is extremely likely to draw an object either too 
large or too small ; this is to be avoided, as one object of microscopic 
examination is to definitely ascertain the size of objects. It is the 
writer's practice when working without sketching to note the measure- 
ments with the eye-piece micrometer. When sketching he makes 
tracings of sufficient at least of the object to give its actual dimensions 
by a process similar in principle to that already described. 

109. Camera Lucida. — For tracing with the microscope an in- 
genious appliance has been invented, which is known as a " camera 
lucida ; " there is also a modification termed a neutral tint camera. 
Space does not permit our describing these, but they fit over the eye- 
piece, and when properly arranged either project the microscope image 
so that it appears to be on the sheet of paper designed for its reception, 
or displaces the image of the paper so as to cause it to be seen apparently 
in the centre of the field of the microscope. In either case the image 
and the surface of the paper are made to coincide. Some cameras are 
constructed on the principle of the image being seen by one eye and the 
paper with the second, while in others both the paper and the image are 
visible to one and the same eye. When using a camera the paper and 
image should, as nearly as possible, be equally illuminated. 

As a preliminary to tracing with the camera, place the stage micro- 
meter in focus, and the microscope and paper in their respective 
positions. These may be any that are most convenient. Then mark on 
the paper the length of the millimetre or fraction of the millimetre, 
and calculate out once for all the magnification in exact number of 
diameters. With the same powers and eye-pieces, and microscope and 
paper in the same relative positions, the magnification is always the same. 
In actual sketching it is usually sufficient to trace in the principal out- 
lines; the details may then be added with sufficient accuracy by the ordi- 
nary method of judging dimensions by the eye, as in freehand drawing. 

The methods of using the microscope having been briefly described, 
directions for its use for special purposes will be given as occasion 
arises. For fuller descriptions of the instrument itself, its accessories 
and the method of using them, the student is referred to one of the 
many excellent works already published on the subject. 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



110. Polarisation Of Light. — There are many substances which 
exert a special action on " polarised light," among these are a variety of 
crystalline compounds, and certain organised bodies. It will be neces- 
sary at this stage to give a short description of the nature of a ray of 
light, and the way in which its character may be altered by the action 
of these substances just mentioned. As is well known, light travels in 
straight lines called rays. The actual motion of such a ray of light is 
somewhat like to that of a sea-wave, or the ripples produced on the 
smooth surface of a pond by throwing a stone therein. In waves, the 
water itself does not move forward, but only the undulating motion of 
the surface ; this is readily seen by floating a cork on the water, each 
little wave in its passage onward simply raises and depresses the cork, 
but leaves it in the same position as it found it. Light then also travels 
in waves, these waves being undulations in a substance filling all space, 
and known by the name of " ether." The waves of light differ re- 
markably in one particular from those on the surface of water ; the 
undulatory motion in the latter is simply up and down, or, to use the 
scientific term, in a vertical plane. If the actual movements of the 
ether in a ray of light could only be rendered visible a much more com- 
plicated motion would be perceived. Just as in the case of the water- 
wave, the particles would move across, or transversely to, the direction 
of the path of the ray. Some of the particles would rise and fall like 
those in the water wave, but others would swing from side to side, or 
horizontically instead of vertically ; further than this, others again 
would vibrate at every intermediate angle. This condition of things is 
expressed in the statement that the undulations of a wave of light are in a 
plane transverse to the path of the ray, and that the ether particles 
vibrate in every direction in that plane. 

For our present purpose it will be sufficient to regard the wave of 
light as composed of two sets of vibrations, the one vertical and the 
other horizontal, and therefore at right angles to each other ; the inter- 
mediate vibrations may be ignored. The character of the undulations 
of a wave of light is not greatly altered by passing through glass, water, 
and many other bodies ; the same does not, however, hold good with all 
transparent substances — of these one of the most striking is a mineral 
named tourmaline. Let two thin plates be cut from a crystal of this 
substance in a certain direction ; on examination each is seen to be 
fairly transparent. Let one be placed over the other and then slowly 
twisted round. In one particular position light passes through them 
both as readily as through either taken singly ; but as one of the pair is 
turned round, less and less light is transmitted; until, when it has been 
rotated through an angle of 90 degrees, no light whatever passes. As 
the revolution is continued, the plates allow more and more light to 
pass ; until, when an angle of 180 degrees has been reached, the combina- 
tion of two plates is again transparent. A further revolution of 90 
degrees once more causes opacity. This peculiar effect is due to the 
fact that tourmaline plates, such as described, permit the passage through 
them of only the vibrations of light in one plane, so that the ray of 
light, after passing through the tourmaline, instead of having 
its vibrations in all directions of the plane has them occurring 



POLARISATION OF LIGHT. 53 

in one direction only ; the ray may then be compared to a 
water wave. Such a ray of light is said to be " polarised," and 
the change effected is termed the "polarisation of light." 

The tourmaline plate may be compared to a sieve composed of a set 
of wires in but one direction. Using this similitude, only those vibra- 
tions, which are in the same direction as the wires of the sieve, succeed 
in effecting a passage. The second tourmaline plate being set so that 
its wires are parallel to those of the first, the light which passed through 
the one succeeds also in passing through the other. But when the 
second tourmaline is turned at right angles to the first, then the light 
which passed through the one is cut off by the other, and so the two 
together refuse to transmit any light whatever. 

Persons who are acquainted with the beautiful mineral known as 
Iceland spar, know that when a single dot is looked at through a piece 
of the spar it is seen double ; this is due to the fact that the spar splits 
the ray of light into two distinct rays ; further, the light of each of 
these sub-rays is polarised in such a manner that the plane of polarisa- 
tion (that is, the direction in which the vibrations occur) of the one ray 
is at right angles to that of the other. When pieces of Iceland spar 
are cut and re-joined in a particular manner, they transmit the one 
only of these two rays, the other being lost by internal reflection within 
the crystal. Such pieces of spar are termed " Nicol's prisms," and may 
be used for the same purpose as the tourmaline plates ; they have the 
great advantage of being composed of material as transparent as glass, 
while the tourmaline is usually only semi-transparent, apart from its 
polarising properties. The first Nicol's prism placed in the path of a 
ray of light is termed the polariser, because it effects the polarisation ; 
the second is known as the analyser, because it enables us to determine 
direction of the plane of the polarised ray. 

Returning again to the similitude of the sieves, suppose that, with 
the two at right angles to each other, it were possible to take the light 
after it had passed through the one, and was thus polarised, and twist 
or rotate its plane of polarisation through an angle of 90° before it came 
to the second, it would evidently then be able to pass through that also. 
Certain substances possess this remarkable property: among those of 
immediate interest in connection with the present subject are starch, 
sugar, and other of the carbohydrates. It is further found that while 
some compounds twist the polarised ray to the right, or in the direction 
of the hands of a watch, others rotate polarised light to the left. If 
two Nicol's prisms were so arranged as to give absolute darkness, and 
then a plate of sugar were placed between them, light would be trans- 
mitted. If the analyser were next turned around in a right-handed 
direction, the point of absolute darkness would again be reached, and 
then by measuring the angle of rotation, the number of degrees through 
which the plane of polarisation of light had been rotated by the sugar 
could be ascertained. Instruments are constructed for the purpose of 
making this measurement with great delicacy, and are termed " polari- 
meters." The exact point at which maximum light and darkness is 
reached, during the rotation of the analyser, cannot be observed with 
great accuracy ; recourse is therefore had to observing some of the other 



54 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

characteristics of polarised light more easily detected by the eye. In 
the analytic section of this work, an explanation is given of the princi- 
ples which guide chemists in the application of the rotation of the plane 
of the polarisation of light by sugar and other bodies to their estimation ; 
a practical description then follows of one of the best forms of polari- 
meters and the method of using it. Eor microscopic purposes a polariser 
is fitted underneath the stage, and an analyser either within the body 
of the tube or over the eye-piece. The object under examination is 
thus illuminated by polarised light. For further information on the 
polarisation of light, the student is referred to Ganot's, or some other 
standard work on physics. 



MINERAL MATTERS. 55 



CHAPTER V. 

CONSTITUENTS OF WHEAT AND FLOUR. 

MINERAL AND FATTY MATTER?. 

111. Construction Of Wheat Grain. — Having given a brief 
outline of the principles and theory of Chemistry, in so far as they are 
more or less connected with the present subject, our next object must 
be to describe the chemical properties of the different compounds found 
in the grain, and to trace them out in the history of the flour and offal. 
The " Cereals," to which wheat belongs, is the name given to the grasses 
which have been cultivated for use as food. The grain, as is of course 
well known, is the seed of the plant ; although not strictly chemical it 
will be well to give here a short description of its various parts. The 
most important portion of the seed is the embryo or germ ; this, which 
is a body rich in fatty matters, is that part of the seed which grows into 
the future plant. The interior of the seed contains a quantity of starch 
and other compounds, designed for the nutrition of the young plant 
when growing. The whole is enclosed in an envelope, made up princi- 
pally of woody fibre, and arranged in a series of coats, one outside the 
other, somewhat like those of an onion, only on a much finer scale. 
During the process of milling, the grain is divided into flour and what 
is technically known as offal. This latter substance, or group of sub- 
stances, includes the germ, bran, pollard, &c. The bran and pollard are 
the different skins of the grain broken up into fragments of various 
sizes. This department of the subject will be dealt with fully in a sub- 
sequent part of the work. 

112. Constituents Of Wheat. — A large number of chemical 
compounds may be obtained from grain : these naturally divide them- 
selves into Mineral or Inorganic Constituents, and Organic Constituents. 
The inorganic portions of wheat consist of water and the mineral bodies 
found in the ash. The organic compounds may be conveniently grouped 
into — fatty matters, starch, and allied bodies having a similar chemical 
composition, and nitrogenous bodies or albuminoids. Of these sub- 
stances the fats have the simplest composition, next come the starchy 
bodies, and lastly, the albuminoids, whose constitution is extremely 
complex. It may be stated as a general rule that the more complicated 
the constitution of a body, the more easily is it broken up into simpler 
compounds : this holds good in the case at present under consideration. 
The fats are not liable to undergo any very radical alteration in chemical 
constitution ; starch changes more readily, while the albuminoids under 
favourable circumstances decompose with great rapidity. 



56 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



113. Mineral Constituents. — The properties of water are already 
sufficiently described : the actual amount present in grain varies from 
about 10 to 15 per cent. In sound wheats and flours there is no per- 
ceptable dampness, the water being chemically combined with the starch, 
which body probably exists in grain as a hydrate. The other mineral 
constituents are usually obtained by heating the powdered grain to faint 
redness in a current of air ; the organic bodies burn away and leave an 
ash consisting of the inorganic substances present. The ash of wheat 
has been made the subject of prolonged investigations and research, 
conducted principally, however, from an agricultural point of view. 
Land being impoverished by the growth of crops, the constitution of the 
ash of wheaten grain and straw is an indication of what mineral matters 
are removed from the soil by wheat crops, and therefore also affords in- 
formation as to what additions have to be made to an exhausted soil in 
order to replenish its necessary mineral components. Lawes and Gil- 
bert have from time to time published elaborate tables of results ob- 
tained on their experimental farm at Rothampsted ; the following table 
is abstracted from a recent communication of theirs to the Chemical 
Society (Chem. Soc. Jour. Vol. XLY., page 305 et seq.) It gives the 
composition of the grain-ash of wheat, grown on the same land, in four 
characteristic seasons — 1852, 1856, 1858, and 1863 ; the land being 
treated with farmyard manure : — 



HARVESTS:— 


1852. 


,856. 


1858. 


1863. 


Weight per bushel of grain, lbs. 


58-2 


58-6 


62-6 


63-1 


Percentage Composition of Ash. 










Iron Oxide, Fe 2 3 , ... 


0-95 


0-86 


0-90 


0-43 


Lime, CaO, 


2-79 


2-53 


2-61 


2-34 


Magnesia, MgO, 


12-77 


11-71 


11-17 


11-41 


Potash, K 2 0, ... 


27-22 


29-27 


31-87 


31-54 


Soda, Na 2 0, ... 


0-45 


0-42 


0-28 


0-66 


Phosphoric Anhydride, P 2 5 , 


54-69 


54-18 


51-88 


52-04 


Sulphuric Anhydride, S0 3 , ... 


0-14 


0-23 


0-75 


0-93 


Chlorine, Cl 2 , ... 


trace 


0-07 


0-06 


trace 


Silica, Si0 2 , ... 

Total, 


0-99 


0-75 


0-49 


0-65 


100-00 


100-02 


100-01 


100-00 



The ash constitutes about 1*5 per cent, of wheat, and about 0-4 per 
cent, of the finished flour, while bran yields from 6 to 7 per cent, of 
ash. It will be noticed that more than half the wheat ash consists of 
anhydrous phosphoric acid; this is principally in combination with 
potash, forming potassium phosphate. The magnesia is also present as 
a salt of phosphoric acid. The greater part of wheat ash, therefore, 
consists of potassium phosphate, and is soluble in water. The phos- 
phates are of importance from their value as articles of food : where 
wheaten flour or bread is almost the sole article of diet, the removal of 
the phosphates during the purification of the flour diminishes its nutri- 



FATTY MATTERS. 57 



tive value. In an ordinary mixed diet, where bread is simply one of 
several articles consumed, this does not apply, as sufficient phosphates 
are always present in other articles of food. 

114. Organic Constituents, Fatty Matters — Of the nume- 
rous organic bodies found in wheat, fat has not been chosen as the first 
to be described because of its importance as a grain constituent, but 
because it has the simplest composition of the organic bodies present, 
and therefore may fitly serve as an introduction to the chemistry of the 
more complicated compounds to follow. All grains contain more or less 
fat; rice has the least quantity, viz. 0*1 per cent. ; maize and oats have 
respectively 4*7 and 4*6 per cent. ; wheat occupies a medium position 
with a percentage of 1*2 to 1*5. The fat of wheat is not equally dis- 
seminated through the grain, but is almost entirely contained in the 
germ and husk or bran. An analysis by Church gives the quantity of 
fat in "fine wheat flour" as 0'8 ; it is, however, doubtful if this analysis 
were made since the time when the problem of degerming flour has re- 
ceived so much attention from the miller. 

It has been already explained that the fats are salts of certain acids, 
with glycerin as a base. They are characterised by their unctuous 
nature and by leaving a greasy stain on paper or linen. Tats are in- 
soluble in water, and from their low specific gravity float on the surface 
of that liquid. On the other hand, all fatty bodies dissolve readily in 
either ether or light petroleum spirit. As food stuffs, the fats occupy 
a high position ; in tables giving the relative nutritive value of different 
articles of food, fat heads the list. If this were the only point to be 
considered, the presence of fats in wheat and flour would be highly ad- 
vantageous. They have, unfortunately, one great drawback, and that 
is that they become rancid on standing. This effect is particularly 
noticeable in flour imperfectly freed from germ. The rancidity is due 
to slow oxidation of certain constituents of the fat ; this change may 
proceed sufficiently far to seriously affect the flavour of the flour, with- 
out the fat as a whole being very greatly changed. The fat of wheat 
is of a light yellow colour, melts at a low temperature, and gradually 
darkens in colour on being kept. This change proceeds rapidly in the 
fat when maintained at a temperature of 70 or 80° C. 

Konig states that the fat of rye, a grain very similar to wheat, has 
the following composition : — 

Per Cent. 

Glycerin, ... ... ... ... 1*30 

Oleic acid, ... ... ... ... 91-60 

Palmitic and stearic acids, ... ... 8*10 

According to Konig, therefore, the fat of rye consists largely of free 
fatty acids, the glycerin present being insufficient to neutralise but a 
small proportion of the acids present. 

Many bakers assert that the fat of flour deadens fermentation, and 
state that greasy flours do not rise anything like so well as do those 
flours from which all oily matters have been removed. It is probable 
that the so-called greasy nature of flours is due not to the presence of 
excess of fat, but to faulty milling or unsound wheats. Either of these 
causes would tend to produce the greasy feel referred to, and would 



58 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

militate against the flour behaving well during fermentation. Fat of 
itself has no injurious action on yeast. 

Experimental Work. 

115. The student who proposes to master for himself the contents of 
this work, should endeavour to verify as many as possible of the 
various statements and descriptions by direct experiment. The follow- 
ing outline of experimental work is intended as a laboratory course of 
study on the subject. 

116. Mineral Constituents. — Take a small quantity of whole 
wheaten meal, heat it to redness over a bunsen in a shallow platinum 
capsule or basin. At first the volatile constituents of the grain burn 
with flame, leaving a black mass of carbon and ash. Continue the ap- 
plication of heat until the carbon entirely burns away leaving behind a 
greyish white ash. To this, when cool, add water • notice that most of 
it dissolves ; add a few drops of hydrochloric acid, filter the solution, 
and make a qualitative analysis of it; test specially for calcium, magne- 
sium, potassium, and phosphoric acid. It is well to test direct for these 
two latter constituents in separate small portions of ash. To test for 
potassium, dissolve up a portion in hydrochloric acid, filter and add a 
few drops of platinum chloride to some of the solution in a watch-glass ; 
the presence of potassium is demonstrated by the formation of the 
yellow precipitate of the double chloride of platinum and potassium. 
Dissolve another portion of the ash in nitric acid, filter and add nitric 
acid and ammonium molybdate solution ; after standing for some time 
in a warm place, phosphoric acid throws down a canary-yellow preci- 
pitate. 

117. Pat. — In a tightly corked or stoppered bottle, shake up together 
some wheat meal and ether, allow the mixture to stand for an hour, 
giving it an occasional shake meanwhile. At the end of that time, 
filter the ether through a paper into a clean evaporating basin and 
allow it to spontaneously evaporate. Notice that it leaves a small 
quantity of fat in the basin. Remember that the greatest care must be 
taken in all experiments with ether to avoid its taking fire. It is best 
to make this experiment in a room where there are no lights. 



THE CARBOHYDRATES. 



59 



CHAPTER VI. 



THE CARBOHYDRATES. 



118. Definition of " Carbohydrate."— This name has been 
applied to a class of bodies composed of carbon, hydrogen, and oxygen, 
in which the latter two elements are present in the same proportion as 
in water, namely, two atoms of hydrogen for every one of oxygen. 
Thus for example, starch contains to the six atoms of carbon, ten atoms 
of hydrogen to five atoms of oxygen. The carbohydrates comprise, 
among their number, bodies differing considerably in physical appear- 
ance and character, but yet exhibiting signs of close chemical relation- 
ship. Subjoined is a table of the more important carbohydrates, together 
with their simplest possible formulae :- 
Cellulose, ... 
Starch, 



Dextrin, . . . 
Maltose, . . . 
Cane Sugar, 
Milk Sugar, 
Glucose, or Grape Sugar, 



C 6 H 10°5' 

C 6 H 10 O 5- 

C 6 H 10 O 5- 

^12-"-22^11' 

^12 H 22^11- 

^12-^-22^11- 

C 6 H 12 (T 



Cellulose, C 6 H 10 5 . 

119. Occurrence and Physical Properties. — This body con- 
stitutes the frame-work or skeleton of vegetable organisms, in which it 
acts as a sort of connective tissue, binding and holding together the 
various parts and organs of plants. Woody fibre consists largely of 
cellulose and one or two closely allied substances. 

The pith of certain plants and also the horny part of certain seeds, 
as " vegetable ivory," are nearly pure cellulose. Manufactured vege- 
table fabrics, as cotton and linen goods, and likewise unsized paper, are 
also cellulose in an almost pure form. Chemically pure Swedish filters 
consist of cellulose with only the most minute traces of other bodies. 

Pure cellulose is white, translucent, of specific gravity of about 1*5, 
and is insoluble in water, alcohol, ether, and both fixed and volatile oils. 
An ammoniacal solution of copper hydrate dissolves cellulose completely; 
this reagent may be prepared by precipitating copper hydrate from the 
sulphate, by sodium hydrate, and then dissolving the thoroughly washed 
precipitate in strong ammonia. This solution dissolves cotton wool, or 
thin filtering paper, forming a sirupy solution ; on the addition of slight 
excess of hydrochloric acid, the cellulose is precipitated in flaky masses; 
these, on being washed and dried, produce a brittle horny mass. This 



60 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

re-precipitated cellulose is not coloured blue by iodine, and still presents 
the same chemical properties as ordinary cellulose. 

120. Behaviour with Chemical Reagents.— Cellulose, on 

being boiled with water under pressure, is converted into a body bear- 
ing some resemblance to dissolved starch, inasmuch as it is coloured blue 
by iodine. The same effect is produced more rapidly by treatment with 
acids. Boiling with dilute sulphuric or nitric acid, or strong hydro- 
chloric acid, breaks up cellulose into a flocculent mass, but without any 
change in composition. Treatment with stronger nitric acid changes 
cellulose into nitro-substitution products called gun cottons or pyroxylin ; 
while that acid, in a yet more concentrated form, oxidises cellulose to 
oxalic acid. By the action of strong sulphuric acid, cellulose is con- 
verted into dextrin. Concentrated solutions of potash or soda also dis- 
solve cellulose, with the formation apparently of the same compound. 
Sulphuric acid, diluted with about half or quarter its bulk of water, has 
a most remarkable action on unsized paper. The paper on being dipped 
in the acid for a few seconds and then washed with weak ammonia, is 
found to be changed into a tough parchment-like material, which may 
be used for many of the purposes to which animal parchment is applied. 
This body is familiar to confectioners, as being sold under the name of 
parchment paper for tying down pots containing jam and other sub- 
stances. Francis has recently found that filter papers on being mo- 
mentarily immersed in nitric acid of density 1'42 are remarkably 
toughened, the product being still pervious to liquids and therefore 
suitable for filtering purposes. He recommends the use of such papers 
for filtering bodies that have to be removed from the paper while wet. 
(See Chem. Soc. Jour., Vol. XLVL, p. 183.) 

121. Existence in Wheat. — The cellulose of wheat exists prin- 
cipally in the bran, but is also found in small quantity disseminated 
throughout the whole of the grain. Flour contains very little cellulose, 
and that little is in an extremely finely divided state. 

122. Composition. — The formula, C 6 H 10 O 5 , is the simplest that 
can be derived from the percentage composition of cellulose, but it is ex- 
tremely probable that the molecule really consists of a number of 
groups of C 6 H 10 O 5 united together. 

Starch, ?zC g H 10 O 5 . 

123. Occurrence. — The starchy matters of wheat are of vast im- 
portance as constituting the greatest portion of the whole seed. Starch 
is not only found in wheat, but also in other seeds ; and in fact in most 
if not all vegetable substances used as food. From whatever source 
obtained, starch has the same chemical composition, but varies some- 
what in physical character. 

124. Physical Character. — Starch, when pure, is a glistening, 
white, inodorous granular powder. If a pinch be taken and squeezed 
between the thumb and finger a peculiar "crunching" (crepitating) 
sound is heard. Starch has a specific gravity of from 1-55 to 1'60. 
Starch is extremely hygroscopic, absorbing moisture with avidity ; in 
the form in which it is usually sold it contains about 18 per cent, of 



THE CARBOHYDRATES. 61 



water. Wheat starch after drying in a vacuum still retains about 11 
per cent of water. Heating in a current of dry air to a temperature of 
110° C. renders it practically anhydrous. 

125. Microscopic Appearance. — The microscope shows starch 
to be composed of minute grains, each having a well denned structure. 
These grains are respectively termed starch cells, granules, or corpuscles. 
Careful examination reveals that each cell consists of an outer coating 
or pellicle formed of a very delicate type of cellulose, to which the name 
" starch cellulose " is applied. This envelope is built up of several layers, 
arranged concentrically one over the other, and contains within its 
interior a substance which may be called starch proper, in distinction 
from the enclosing matter. This starch proper is also termed " starch 
granulose " or " amy lose". On careful examination these separate coats 
appear as a series of more or less concentric rings, having for a nucleus 
a dark spot or cross, termed the " hilum." The actual size and shape 
of starch Cells varies with the source from which the starch is derived \ 
thus the grains of starch from potatoes are comparatively large, while 
those of rice are extremely minute. When examined by polarised light 
certain starches exhibit characteristic appearances — these are referred 
to in detail in the table following. A description of the phenomena of 
polarisation is given in chapter IV. It is possible in many instances to 
determine the origin of a sample of starch by its microscopic character- 
istics ; it follows that impurities may similarly be detected ; also, as all 
vegetable adulterants of flour contain starch, admixture of other grains, 
as maize, rice, &c, is in this manner revealed. 

Microscopic Characters of Various Starches. 

126. Wlieat.- — Wheat starch is extremely variable in size, the dia- 
meter of the corpuscles being from 0*0022 to 0*052 m.m. (0*00009 to 
0*0019 inch). Many observers point out that medium sized granules 
are comparatively absent. The grains are circular or nearly so, being 
at times somewhat flattened. The concentric rings are only seen with 
difficulty ; the hilum is not so visible as in certain other starches. 
Polarised light shows a faint cross. In old samples of wheat or flour 
the granules show cracks and fissures : this applies more or less to all 
starches. 

127. Barley. — Granules more uniform in size than those of wheat> 
also somewhat smaller; average diameter 0*0185 m.m. (0*00073 inch); 
a few exceptionally large granules may be found measuring as much as. 
0'07 m.m. Shape, slightly angular circles. Concentric rings and 
hilum either invisible or only seen with difficulty. 

128. Rye. — Diameter of granules from 0*0022 to 0*0375 m.m. 
(0*00009 to 0*00148 inch). Taking a whole field, the average size of 
granules is usually somewhat higher than those of wheat. Shape, gran- 
ules are almost perfectly round, here and there show cracks. Con- 
centric rings and hilum only seen with difficulty. 

129 Oats.— Diameter of granules, 0*0044 to 0*03 m.m. (0-00017 
to 0*00118 inch). Granules are angular in outline, varying from three 
to six-sided. 



62 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

130. Maize. — Diameter of granules, average size, 0-0188 m.m. 
(0.00074 inch). Shape, from round to polyhedral, mostly elongated 
hexagons, with angles more or less rounded. Concentric rings scarcely 
visible, hilum star-shaped. 

131. Rice. — Diameter of granules from 0*0050 to 0*0076 m.m. 
(0*0002 to 0*0003 inch). Granules are polygonal in shape, mostly 
either five or six-sided, but occasionally three-sided. Are usually 
seen in clusters of several joined together. A very high magnifying 
power shows a starred hilum. 

132. Potatoes. — Diameter of granules from 0*06 to 0*10 m.m. 
(0*0024 to 0*0039 inch). The granules vary greatly in shape and size; 
the smaller ones are frequently circular ; the larger grains are mussel or 
oyster shaped. The hilum is annular, and the concentric rings incom- 
plete ; but especially in the larger granules, clear and distinct. The 
rings are distributed round the hilum in very much the same way as 
the markings show on the outside of a mussel shell. With polarised 
light a very distinct dark cross is seen, the centre of which passes 
through the hilum. 

133. Canna Arrowroot, or Tous les mois. — Diameter of 

granules varies from 0*0469 to 0*132 m.m. (0*0018 to 0*0052 inch). 
The shapes differ considerably, from round to more or less elongated 
ovals. The hilum is eccentric ; the rings are incomplete, extremely 
fine, narrow and regular. Under polarised light a more distinct cross 
is seen than with the potatoes. 

For particulars given in the above table the writer is in part indebted 
to Muter's classification, as quoted in Blyth's Composition and Analysis 
of Foods. 

134. Solubility Of Starch. — Starch is insoluble in cold water, 
and cannot be dissolved by any known liquid without change : this fol- 
lows from its having a definite organic structure; when this is destroyed, 
.as must of necessity be the case whenever a solid is rendered liquid, it 
cannot by any artificial means be again built up in the same form. 

As previously stated, the starch granules consist of an outer envelope 
of cellulose, enclosing what is termed "amy lose," or starch proper. 
This latter body is soluble, and although pure starch in the granular 
form yields no soluble substance to water, yet if the cellulose envelopes 
be ruptured by mechanical means, it is then found that on treatment 
with water at ordinary temperatures a soluble extract is obtained. 
When, however, starch is subjected to the action of boiling water a 
marked change ensues : under the influence of heat the little particles 
in the interior, by swelling, burst the containing envelope, and dissolv- 
ing in the water form a thick and viscous liquid, which on cooling, if 
sufficiently concentrated, solidifies into a gelatinous mass. This solu- 
tion of starch is somewhat cloudy, owing to the undissolved particles of 
starch cellulose remaining in suspension. These may be, in great part, 
removed by filtration. 

This bursting of the starch granules is frequently spoken of as the 
" gelatinisation " of starch. The temperature at which this change 
occurs varies with the nature and origin of the starch. 



THE CARBOHYDRATES. 



63 



The following table gives, on the authority of Lippman, particulars as 
to the gelatinising temperatures of starch from different sources : — 



Source of Starch. 


Granules 


Gelatinisation. 


Swollen. 


Commenced. 


Completed. 


. °c. 


°F. 


°c. 


°F. 


°c. 


°F. 


Barley, 
Maize, 

Rye, 

Potato, 

Rice, 

Wheat, 


37-5 

50-0 
45-0 
46-1 
53-8 
50.0 


99-5 
122-0 
113-0 
115-0 
129-0 
122-0 


57-2 
55-0 
50-0 
58-3 
58-3 
65-0 


135 
131 
122 
137 
137 
149 


62-2 
62-2 
55-0 
62-2 
62-2 
67-2 


144 
144 
131 
144 
144 
153 



Wittmack disagrees with these results in so far as they concern rye 
flour, which he states commences to gelatinise at 60° C. (The Miller, 
Dec. 1, 1884; p. 798.) 

135. Action of Caustic Alkalies on Starch. — Treatment 

with cold dilute solutions of potash or soda causes starch granules to 
swell enormously ; the volume of starch grains may thus be made to 
increase 125-fold. This reaction also serves for the differentiation of 
the various starches. H. Symons recommends the use of soda solutions 
of different strengths : a small quantity of the starch is shaken up in a 
test-tube for ten minutes with one of the soda solutions, and then a drop 
of the liquid is examined under the microscope. The 
table of results thus obtained: — 

A few starch granules 
dissolved in a solution of 

Potato, 0-6 per cent. 
0-6 „ 
0-7 



Oats, 
Wheat, 
Maize, 
Rice, 



The greater number 
dissolved in a solution of 

0'7 per cent. 

0-8 „ 
0-9 



following is a 



All 



0-8 
1-0 



1-0 
1-1 



dissolved in a solution of 

0-8 per cent. 
1-0 „ 
1-0 „ 

I'l „ 
1-3 



136. — Action Of Zinc Chloride. — Treatment with zinc chloride 
also causes a remarkable swelling of the granules of starch ; this re- 
action, when viewed under the microscope, serves admirably to show the 
structure of the corpuscles. Some concentrated solution of zinc chloride 
is tinged with a trace of free iodine. A few grains of the starch are 
placed on a glass slide, together witli a small drop of this solution. No 
change is observed until a little water is also added. They then assume 
a deep blue tint, caused by the iodine, as explained in a subsequent 
paragraph, and gradually expand. A frill-like margin developes round 
the granule, the foldings of this frill open out in their turn, until the 
granules at last swell up to some twenty or thirty times the original 
volume, and then appear as limp looking sacs. These changes, so far 
as can be seen, are not accompanied by any expulsion of the inner 
contents of the cell. 

137. Properties of Starch in Solution.— A solution of starch 

is colourless, odourless, tasteless, and perfectly neutral to litmus. 



64 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Starch is a highly colloid body, and can be readily separated by dialysis 
from crystalline substances. On evaporating a solution of starch, it 
does not recover its original insolubility. Starch solution causes right 
handed rotation of polarised light. Starch amylose is insoluble in 
alcohol, and may be entirely precipitated from its aqueous solution by 
the addition of alcohol in sufficient quantity. Soluble starch is coloured 
an intense blue by the addition of iodine in extremely small quantities. 
This blue colouration disappears on heating the solution, but reappears 
on its being cooled. This reaction is exceedingly delicate, and is char- 
acteristic of starch. For the purpose of this test, the iodine may be 
dissolved in either acohol or an aqueous solution of potasium iodide ; for 
most purposes preferably the latter. For the occurrence of this reaction, 
the presence of water is apparently essential ; for if wheaten flour be 
moistened with an alcoholic solution of iodine no colouration is produced 
other than the natural brownish yellow tint of tincture of iodine. But 
with a potassium iodide solution the flour assumes a blue colour so in- 
tense as to be almost black. The iodine colouration of starch is only 
caused by free iodine, not by iodine compounds. Potash or soda in 
solution, when added to dissolved iodine, immediately combine therewith 
to form iodides and iodates ; consequently, the iodine test for starch is 
inapplicable in an alkaline medium. In case a solution to be tested for 
starch, is alkaline to litmus, cautiously add dilute sulphuric acid, until 
neutral or very slightly acid ; the test for starch may then be made. 
The only compounds likely to interfere with the iodine reaction for 
starch are some of the dextrins ; these bodies give a brown colouration 
with iodine, but unless present in large quantities do not prevent the 
detection of starch. Iodine combines with starch more readily than 
with dextrin, consequently the iodine should in such cases be added in 
very small quantities at a time, when the blue colouration due to the 
starch will appear before the brown tint produced by dextrin. 

Starch does not cause a precipitate with Fehling's solution, that is, 
it does not reduce an alkaline solution of copper sulphate in potassium 
sodium tartrate. (See paragraph 144, on maltose.) 

Starch under the influence of heat, and readily, when treated with 
certain other bodies, is transformed into others of the carbohydrates. 

138. Preparation and Manufacture of Starch.— For ex- 
perimental purposes, starch can readily be obtained from wheaten flour 
by first preparing a small quantity of dough ; this is then wrapped up 
in a piece of fine muslin, or bolting silk, and kneaded between the fingers 
in a basin of water. The milky fluid thus produced deposits a white 
layer of starch on the bottom of the vessel, which may be carefully air- 
dried. The starch of barley and the other cereals may be obtained in 
a sufficiently pure form for microscopic study in the same manner. 
Potatoes require to be first scraped, or rubbed through a grater, into a 
pulp ; this pulp must then be enclosed in the muslin and the starch 
washed out. 

On the manufacturing scale, starch is obtained from wheat and other 
grains by first coarsely grinding and then moistening the meal with 
water. This is allowed to stand, and after three or four days fermenta- 
tion sets in, more water is then added and the putrefactive ferment a- 



THE CARBOHYDRATES. 65 



tion allowed to proceed for some three or four weeks. By the end of 
this time the gluten and other nitrogenous matters are dissolved. They 
are then readily separated from the starch by washing, after which the 
starch is dried. Starch is now largely manufactured from rice by a 
process in which the grain is subjected to the action of very dilute 
caustic soda, containing about 0*3 per cent, of the alkali ; this reagent 
dissolves the nitrogenous bodies and leaves the starch unaltered. The 
so-called " corn flour " is the starch of maize prepared after the same 
fashion. Potato starch is obtained by first rasping the washed potatoes 
into a pulp by machinery ; the pulp is next washed in a sieve, the starch 
is carried through by the water, and after being allowed to subside is 
dried on a tile floor at a gentle heat. 

Dextrin, C 6 H 10 O 5 . 

1 39. Occurrence. — Dextrin is principally known a3 a manufac- 
tured article, but also occurs in small quantities as a natural constituent 
of wheat and most bodies containing starch. 

140. Physical Character. — In appearance, dextrin is a brittle 
transparent solid, very much resembling the natural gums, as gum ara- 
bic. It is colourless, tasteless, and odourless. Dextrin is a colloid body, 
and is very soluble in water, and also in dilute alcohol : it is insoluble 
in absolute alcohol, by means of which it may be precipitated from its 
solutions. Dextrin is also insoluble in ether. Surfaces moistened with 
a solution of dextrin, and then allowed to dry in contact with each 
other, adhere firmly. Commercial dextrin has usually a more or less 
brown tint from the presence of caramel in small quantity. 

141. Preparation . — Dextrin is usually prepared by the action of 
heat, with or without certain reagents, on starch. The starch may be 
maintained at a temperature of about 150° C. until it assumes a brown 
colour : treatment with water then dissolves out dextrin in an impure 
form. If the starch be first moistened with water containing a minute 
quantity of nitric acid, the change proceeds much more rapidly ; the 
starch should in this case be heated to about 200° C. The substance 
thus yielded is that known as British gum, and is largely used for sizing 
calicoes and other purposes in commerce. If starch solution be boiled 
with dilute sulphuric acid until it no longer gives a blue colouration 
with iodine, dextrin will be found in the solution, but mixed with 
maltose. Certain nitrogenous bodies also possess the power of con- 
verting starch into dextrin and maltose. 

1 42. Chemical Character — Dextrin almost certainly consists of a 
mixture of polymeric bodies of closely similar chemical character. These 
several dextrins are separated into two groups by their difference in be- 
haviour when treated with iodine solution. The members of one of 
these groups, known as " erythro-dextrins, " strike a reddish-brown 
colouration on treatment with iodine ; the others, which are classified 
as " achroo-dextrins," yield no colouration when iodine solution is 
added. Dextrin has a powerful action on polarised light, twisting the 
ray to the right : its name is derived from this property. A solution of 
dextrin, in some respects, resembles one of starch ; they are, however, 

F 



66 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

distinguished by the dextrin giving no blue colour when treated with 
iodine. Dextrin exercises no reducing action on Fehling's solution : in 
this respect, its behaviour is similar to that of starch. 

The Sugars — Maltose, Cane Sugar, Milk Sugar, and Glucose. 

143. General Properties. — The sugars are a subdivision of the 
class of bodies known as carbohydrates ; they are characterised by 
having a more or less sweet taste, and are soluble in water. Many are 
natural products occuring both in the animal and vegetable kingdom. 

144. Maltose, 12 H 22 O 11 . — This body occurs in company with 
dextrin in starch solutions, which have been treated with dilute sul- 
phuric acid until the solution no longer yields a blue colouration with 
iodine. It forms a most important constituent of malt extract, amount- 
ing to from 60 to 65 per cent, of the total solid matter. In the pure state, 
maltose consists of small hard crystalline masses or minute needles, 
which are soluble in water and dilute alcohol. Maltose, being a crystal- 
line body, may be separated from dextrin by dialysis, and also by preci- 
pitating the dextrin by means of strong alcohol. A solution of maltose 
causes a right-handed rotation of a ray of polarised light. Maltose 
gives no colouration with iodine, but in common with certain other of 
the sugars, exercises a reducing or deoxidising action on some metallic 
salts. This reducing action is most commonly tested by means of the 
reagent known as " Fehling's solution." This consists of sulphate of 
copper, tartrate of potassium and sodium, and sodium hydrate. If 
sodium hydrate be added to a solution of copper sulphate, a precipitate 
of copper oxide, CuO, combined with water, is thrown down ; the sodium 
and potassium tartrates redissolve this and form a deep blue solution, 
which may be boiled for some minutes without alteration. Now certain 
varieties of sugar reduce the CuO to Cu 2 ; that is, they take away 
oxygen, the change being represented by 2 CuO = Cu 2 + 0. The oxy- 
gen is taken by the sugar, and for our present purpose need not be 
traced further. The Cu 2 0, or copper sub-oxide, thus formed is insoluble 
in the Fehling's solution, and hence is precipitated, first as a yellow and 
then as a brick-red powder. 

145. Cane Sugar, 12 H 22 O n . — Cane sugar is widely spread in 
nature, it is found in certain roots, as beet-root, in the sap of trees, as 
the maple, and in the juice of the sugar cane. These natural solutions 
are first purified, and then the sugar obtained by crystallisation. The 
sugar found in perfectly sound wheat is either identical with, or closely 
allied to, cane sugar. Pure cane sugar is colourless, odourless, and 
soluble in water, to which it imparts a sweet taste. Boiling water dis- 
solves sugar in all proportions, while cold water dissolves about three 
times its weight. Sugar is insoluble in absolute alcohol, ether, chloro- 
form, and petroleum spirit, but is sparingly soluble in rectified spirits 
of wine. The purest commercial form of sugar is that sold by the 
grocers as " coffee sugar," and consists of well-defined crystals about 
three-sixteenths of an inch across. This, when dried at 100° C, to expel 
any water that may be present, is sufficiently pure for most experimental 
work with sugar, A solution of cane sugar exercises a right-handed 



THE CARBOHYDRATES. 67 



rotation on a polarised ray of light. Cane sugar produces no colouration 
with iodine, neither does it cause any precipitate in Fehling's solution. 
By the action of heat, cane sugar melts, and if then allowed to cool, forms 
the solid, termed "barley-sugar;" a prolongation of the heat results in 
giving the sugar a deeper colour. Many sweetmeats consist of sugar 
thus treated. The darkening in colour is due to the fact that at mode- 
rately high temperatures (210° C. = 410° F.) sugar begins to undergo 
decomposition. Watery vapour and traces of oily matter are evolved, 
leaving behind a substance soluble in water, to which it imparts a rich 
brown tint. The characteristic sweet taste of sugar has then disap- 
peared, and the liquid is no longer capable of fermentation by yeast. 
The change has resulted in the formation of a brown substance, termed 
caramel, to which the formula C 12 H 18 9 has been given. Caramel is, 
however, rather a mixture of bodies, than a definite chemical compound. 
The browning of dextrin and starch when heated is also due to the 
formation of caramel. 

146. Milk Sugar, C5 12 H 22 11 . — This sugar is principally of interest, 
as being that present in milk, which contains quantities of it, varying 
from 4 to 5 per cent. 

It will be noticed that the three sugars — maltose, cane sugar, and 
milk sugar have all the same formula. 

147. Glucose or Grape Sugar, 6 H 12 O 6 . — Several modifications 
of glucose exist : of these, two only are of importance in connection 
with the present subject, viz., dextrose or dextro-glucose, and lcevulose 
or lsevo-glucose. 

148. Dextrose Or Dextro-Glucose. — This form of sugar exists 
as a natural product in the juices of many fruits, notably the grape and 
sweet cherry. The former yields about 15 per cent, of grape sugar. 
Dextrose is also found in large quantity in the urine of diabetic patients ; 
some doubt exists as to whether this sugar is absolutely identical with 
the dextrose of fruits. Dextrose, when pure, occurs in crystalline 
masses, it has a sweet taste ; but, weight for weight, possesses much 
less sweetening action than does cane sugar. A solution of dextrose 
exercises a right handed rotation on a ray of polarised light. Among 
the sugars, dextrose is specially noticeable for the great ease with which 
it undergoes alcoholic fermentation. Like maltose, dextrose exercises a 
reducing action on Fehling's solution, producing a red precipitate of 
cuprous oxide. 

149. Lcevulose Or LoGVO-GluCOSe. — This sugar occurs in com- 
pany with dextrose in certain fruits, and also in honey. Lcevulose is 
non-crystallisable, possesses greater sweetening power than dextrose, 
and offers more resistance to alcoholic fermentation. A solution of loevo- 

jlucose exercises a left handed rotation on a ray of polarised light, thus 



distinguishing it from dextro-glucose ; the two names are based on the 
respective right and left handed rotary power of these glucoses. Lcevo- 
and dextro-glucose both act similarly on Fehling's solution. 

150. — Commercial Glucose. — Glucose, in a more or less pure 
form, is largely manufactured for commercial purposes. Under the 
names of " saccharum," " invert sugar," &c, it is used as a substitute 



68 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

for malt by brewers and distillers. Various forms of confectionery and 
fruit jams contain glucose as an important constituent. Glucose occurs 
in two forms in commerce, the one is a thick and almost colourless 
syrup, the other is a hard crystalline body, varying in colour from 
almost white to pale brown. Glucose is usually made from starch, by 
the action of heating with dilute sulphuric or oxalic acid. For the 
purpose, either maize or rice is usually selected. Subjoined are some 
analyses of commercial glucose, which were quoted at a lecture given 
before the Society of Arts, by W. G. "Valentin : — 





Brown, very 


Soft, straw- 




hard English. 


coloured French. 


Glucose, C 6 H 12 6 , 


... 80-0 


58-85 


Maltose, C 12 H 22 113 


none. 


14-11 


Dextrin, C 6 H 10 O 5 , 


none. 


1-70 


Other carbohydrates and traces ) 
of albuminoids, J 


... 8-20 


9-38 


Mineral matter, 


... 1-30 


1-40 


Water, 


... 10-50 


14-56 



100-00 100-00 

The glucose in these commercial products is a mixture of dextrose 
and lcevulose. Cane sugar is also converted into a mixture of dextrose 
and lcevulose by the action of acids ; it is then sold under the name of 
"invert sugar ; " the reason for this name is that such sugar rotates the 
ray of polarised light to the left instead of to the right, as does normal 
cane sugar. 

151. Maltodextrin, \ , n l \r ' 2 ' 2 r\ ir — Recent researches of Brown 

( V°12- tJ 20 U 10/'2 

and Morris indicate the existence of a carbohydrate having the above 
composition, and which they have termed " malto-dextrin," from the 
supposition that it consists of a combination of maltose and dextrin. 
(Chemical Society's Journal, Vol. XLVI, page 527, et seq.). 

Experimental Work. 

152. Cellulose. — Mix in a moderate sized beaker about 5 grams of 
wheat meal, with 150 c.c. of water, and 50 c.c. of a live per cent, solu- 
tion of sulphuric acid ; and set the beaker in a hot water bath for half- 
an-hour, giving its contents an occasional stir. At the end of that 
time add 50 c.c. of a twelve per cent, potash solution, and set the beaker 
in the bath for another half hour. Observe that a residue remains ; 
allow this to subside, and wash it by decantation. Finally, transfer it 
to a filter, and let it drain. The substance thus obtained consists of 
the cellulose or woody fibre of the wheat. Add iodine solution to a 
portion, and notice that it produces no blue colouration. 

It is assumed that most of the students who go systematically through 
this course of experimental work will do so in a regularly appointed 
laboratory : they will there find the solutions of sulphuric acid and 
potash above referred to ready made up for use. Full directions for 
their preparation, and also of other special reagents required, are given 
in the chapters on analytic work toward the end of the book. Unless 



THE CARBOHYDRATES. 



69 



he has not access to such solutions, the student need not at this stage 
of his work trouble to specially prepare them. 

153. Microscopic Examination of Starches. — Take a small 

quantity of either wheat meal, or flour, and make it into a dough. Tie 
this Up into a piece of muslin or bolting silk, and knead in a small cup 
or glass with water ; the starch escapes, giving the water a milky ap- 
pearance, while the gluten arid bran remain behind in the muslin. 
Clean an ordinary microscopic glass slide and cover, shake the starchy 
water and place a minute drop on the slide, lay on the cover, press it 
down gently, and soak up any moisture round its edge with a fragment 
of blotting paper. Place the slide on the microscope stage, and focus 
the instrument, using first the inch and then a quarter or eighth objec- 
tive. The separate starch cells are then plainly seen. Trace in a few of 
the cells on paper, with a camera lucida, and sketch in any points of de- 
tail. Measure one or two of the cells with the eye-piece micrometer, 
and mark their dimensions on the drawing. 



"*>©% 



Q^^QQ 







©$M£) 



h 






<§ ° 





6 



QQ 35 






e/T fo<3> 





ft/tttf»h.B 



FIG. 3. — MICROSCOPIC SKETCHES OF VARIOUS STARCHES, MAGNIFIED ABOUT 
87 DIAMETERS, 
a, Barley. £, Rice, c, Potato, d, Wheat, e, Maize, f, Rye. 

Figure 3 is a fac-simile of such a working sketch as the student should 
himself make while studying starches under the microscope. Most of 
the microscopic sketches given in this work are purposely fac-similes of 
actual students' drawings rather than finished engravings. It is hoped 
that such sketches will answer the double purpose of demonstrating to 
the reader the essentials of whatever is being examined, and at the 
same time will serve the student as examples of such drawings as should 
appear in his own note-book. 



70 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Take a small quantity of the flours, respectively of barley, rye, rice, 
and maize, wash out the starch from each and examine microscopically 
in precisely the same manner as with the wheat, making drawings in 
each case. A little corn flour, being practically pure maize starch, may 
be used instead of maize flour. Cut a potato in halves, and with a sharp 
knife scrape off a little pulpy matter from the cut surface, transfer to 
a slide, and examine with the microscope. 

Notice in each case the relative sizes of the granules, and compare 
their shapes. Examine for the hilum and also observe the rings. If 
the microscope be fitted with polarising apparatus, study the various 
starches under polarised light. 

154. Examination of Mixed Starches. — With separate por- 
tions of wheat flour, mix respectively small quantities of rice meal, and 
corn flour. As before, knead the starch out of each and examine the 
milky fluid for the foreign starches. Notice in the one case the very 
small rice starch granules, and in the other the somewhat larger maize 
starch granules interspersed among those of the wheat. 

155. Gelatinisation of Starch. — Heat separate quantities of 
one gram of the starches of wheat, rye, maize, rice, and potato in 50 c.c. 
of water ; and notice the temperature at which the liquids commence 
to thicken through gelatinisation of the starch. The experiment is 
conducted in the following manner. 




FIG. 4. — APPARATUS FOR DETERMINING TEMPERATURE OF GELATINISATION 

OF STARCH. 

Place a moderately large beaker on a piece of wire gauze over a 
tripod, as in figure 4. Take several small beakers or test tubes, and 
attach to each a wire hook, so that they may be hung over the edge of 
the large beaker. Fill this large beaker with water, and use it as a 
water bath. Put the starch to be tested, together with the requisite 
quantity of water, in one of the small beakers, and suspend it in the 
water bath; under which place a lighted bunsen. While the small 



THE CARBOHYDRATES. 71 



beaker is thus being heated, stir its contents with a thermometer, and 
note the temperature at which the first appearance of geiatinisation is 
detected ; instantly remove the beaker and plunge it into a vessel of 
cold water. When cold, examine a little of the paste with the micro- 
scope, and notice whether or not many of the granules remain unaltered. 
Make a second experiment with the same starch, arresting the temper- 
ature at 2° hotter or colder, according to the degree of geiatinisation 
revealed by the microscope on the first trial. All the starches specified 
are to be tested in the same manner. Wittnack uses this test as a 
means of detecting rye as an adulterant of wheat flour. He removes 
the beaker containing the sample as soon as it reaches 61° C. ; he then 
finds that the heat of the sides is sufficient to raise the temperature to 
62'5° C. At this temperature, Wittnack states that the rye starch 
granules nearly all puff up and burst, while those of wheat are scarcely 
affected. The appearance of each, as revealed by the microscope, is 
shown in figures 5 and 6. 









FIG. 5 —STARCH GRANULES OF RYE, NEARLY DISSOLVED AT 62'5° C. 

ole^ooyo 

FIG. 6.— STARCH GRANULES OF WHEAT, SCARCELY AFFECTED AT 62*50 C. 



72 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

For a full description of Wittnack's mode of testing, the reader is 
referred to his essay on rye and wheat flour, published in The Miller in 
October and following months of the year 1884. For figures 4-6, the 
author is indebted to the courtesy of the proprietor of that journal. 

156. Action of Caustic Alkalies, and Zinc Chloride, on 

Starch. — Prepare a set of solutions of caustic soda of the strength 
described in paragraph 135. To do this, weigh out 10 grams of caustic 
soda, dissolve in a small quantity of water, and then make up the 
volume to 100 c.c. in a measuring flask (see chapter XIX) ; this gives 
a 10 per cent, solution. From this solution, the weaker ones are pre- 
pared by mixing with water in the requisite proportions. For the 0'6 
per cent, solution, take 6 c.c. of the standard soda, pour them into the 
clean 100 c.c flask, add water up to the graduation mark, and shake up ; 
for the 0'7 per cent, solution, take 7 c.c, and so on for the others. The 
soda solution should be measured from a burette ; this also is described 
in chapter XIX. With these solutions, treat small quantities of the 
various starches exactly as described in paragraph 135, and examine 
under the microscope. 

Next place a few granules of starch, together with a little water, on a 
slide under a cover, and focus under the microscope. Take a drop of 
caustic soda solution on the end of a pointed glass rod, and drop it as 
close as possible to the outside edge of the cover, so that it may freely 
run in under. Watch carefully the changes which occur in the starch 
as the granules are attacked by the soda solution. 

Prepare some solution of zinc chloride, and add a trace of free iodine, 
as described in paragraph 136. Mount some starch on a slide with a 
little of this solution ; run in a small quantity of water at the edge of 
the slide, and watch the occurence of the changes referred to. 

157. Reactions Of Starch Solution. — Gelatinise a little starch 
by heating it with water in a test tube or small beaker placed in the 
hot- water bath ; then let the solution cool. 

Dissolve some iodine in alcohol, and aqueous solution of potassium 
iodide, respectively. In each case use sufficient iodine to just give a 
sherry tint to the solution. Add some of either of these solutions (that 
in alcohol is commonly a " tincture ") to a small quantity of the solu- 
tion of starch ; notice the blue colour produced. Heat the solution, 
and then allow it to cool ; observe the disappearance and gradual 
reappearance of the colour. 

Render a portion of the starch solution alkaline by the addition of 
caustic soda or potash : to one portion of this solution add iodine ; 
notice that no colouration is produced. To the other, add dilute sul- 
phuric acid until the solution is slightly acid to litmus paper. Then 
add some iodine solution, and observe that the normal blue colour is 
produced. Add respectively, solution of iodine in potassium iodide, and 
the tincture of iodine, to separate small portions of flour ; notice the 
dark blue colour produced in the first instance, and the sherry tint in 
the second. To the second portion add a little water ; the dark blue 
colour at once appears. Mount a minute portion of flour on a slide 
with iodine solution ; examine under the microscope and notice the blue 



THE CARBOHYDRATES. 73 



colouration of the starch granules, while other constituents of the flour 
remain comparatively uncoloured. 

1 58. Dextrin. — Render some water faintly acid by the addition of 
a small quantity of nitric acid ; with this, moisten some starch in a 
porcelain dish, and maintain it at a temperature of 200° C. in a hot-air 
oven for about two hours. The hot-air oven is usually made of copper, 
and is heated by means of a bunsen placed underneath ; through a hole 
in the top a thermometer is fixed so as to show the temperature. Before 
using the oven, regulate the temperature by turning the bunsen partly 
on or off until the thermometer remains steadily within say 10 degrees 
of 200. The moistened starch must not rest direct on the bottom of 
the oven : it may be placed on a small tripod made by turning down 
the wires of an ordinary pipe-clay triangle. 

Treat this heated starch with hot water, and filter ; a yellowish-brown 
gummy solution is obtained. To a portion, add iodine solution ; notice 
that no blue colouration is produced, but instead a reddish-brown tint ; 
starch, therefore, is absent. The reddish-brown colour is due to the 
presence of erythro-dextrins. From another portion of the solution, 
precipitate the dextrin by adding strong alcohol ; filter and wash the 
precipitate with alcohol, dissolve in a little water and reserve for a 
future experiment. Use a little of the solution for fastening together 
pieces of paper ; notice that it exhibits the ordinary properties of 
gum. 

159. Maltose and other Sugars.— Take from 5 to 10 grams of 

ground malt, and mix with ten times the quantity of water, place the 
mixture in a beaker arranged in a hot-water bath, and keep it at a 
temperature of 60° C. for half-an-hour : this may be done by turning 
down the flame, or altogether removing it from time to time. The 
temperature may range from 55 to 65° C, but must not be allowed to 
go above the latter. At the end of the half -hour, raise the temperature 
to the boiling point for five minutes, and then filter ; the resultant 
liquid is a solution of maltose and dextrin, and may be used for experi- 
ments on maltose. 

Prepare solutions of the following substances, and test them with 
Fehling's solution — (1), starch; (2), the re-dissolved alcoholic precipi- 
tate of dextrin ; (3), aqueous extract of malt ; (4), cane sugar, and (5), 
commercial glucose. 

Set some distilled water boiling in a flask or large beaker for half-an- 
hour. Take 20 c.c. of the mixed Fehling's solution (see Chapter 
XXI V.), add equal quantity of the boiled distilled water, and set in 
boiling hot-water bath for ten minutes ; notice that no precipitate is 
produced. Heat five separate portions of 20 c.c. of Fehling's solution, 
and 20 c.c. of water to the boiling point, and add respectively 20 c.c. of 
the starch and other solutions previously prepared. Let them all stand 
in the hot-water bath for ten minutes : at the end of that time, some of 
the solutions will probably be decolourised, with the deposition of a 
copious red precipitate, while others will remain unchanged. The 
results should be as follows : — 

Starch — No precipitate. 



\/ 



74 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Dextrin — No precipitate. (Practically, there is usually a very slight 
precipitate, owing to difficulty in thoroughly washing the 
dextrin free from maltose). 

Maltose — Red precipitate. 

Cane sugar — No precipitate. 

Glucose — Red precipitate. 



TRANSFORMATIONS OF THE CARBOHYDRATES. 75 



CHAPTER VII. 

TRANSFORMATIONS OF THE CARBOHYDRATES. 

160. It has already been incidentally mentioned that starch may 
readily be converted into dextrin and maltose; with regard to the 
carbohydrates generally, one of their special characteristics is, that the 
less hydrated members of the series are easily changed to those con- 
taining a higher proportion of hydrogen and oxygen. In consequence 
of the great importance of these transformations, they will require to be 
dealt with fully. The present chapter will, therefore, give particulars 
of the nature of these changes, the agents by which they are effected, 
and the conditions which are favourable or unfavourable to their 
occurence. 

161. Hydrolysis. — As the mutations of the carbohydrates consist 
of the addition of the elements of water to the atoms previously present 
in the molecule, it has been proposed to include these changes under the 
general term " hydrolysis." Hydrolysis is, therefore, denned as a 
chemical change, consisting of the assimilation, by the mole- 
cule, of hydrogen and oxygen in the same proportions as they 
exist in water ; and resulting in the production of a new 
chemical compound or compounds. Those bodies capable of pro- 
ducing hydrolysis are termed "hydrolysing agents " or " hydrolytics." 

162. Hydrolytic Agents. — These bodies include oxalic and 
dilute hydrochloric and sulphuric acids. Commencing with soluble 
starch, the acids mentioned possess the power of converting that body 
first into dextrin and maltose, then into glucose. The acid hydrolytics 
also transform cane sugar into glucose. There is another most important 
group of hydrolysing agents ; these consist of certain soluble bodies of 
organic origin, and among them may be mentioned human saliva, 
filtered aqueous infusions of yeast, flour, bran, and malt. Chemical 
research shows that in each case hydrolysis is due to the nitrogenous 
constituents of these various agents. In several instances the active 
principle has either been isolated or obtained in a very concentrated 
form ; it is not known, however, with certainty whether these bodies 
are definite chemical compounds, or whether they are only mixtures of 
certain nitrogenous bodies in a particularly active state. The following 
are the names that have been given to active principles obtained from 
the hydrolytics above mentioned : — 

Substance. Name of hydrolysing constituent. 

Human saliva. Ptyalin. 

Yeast. Zymase or Invertin. 



76 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Substance. Name of hydrolysing constituent. 

Flour, Bran (more especially Cerealin. 

the latter). 

Malt. Diastase. 

Of these substances, the active hydrolysing agent of malt has been the 
most carefully examined : unlike the acids, diastase is incapable of con- 
verting starch further than into dextrin and maltose. Zymase trans- 
forms both maltose and cane sugar into glucose, but has very little 
action on dextrin. Notwithstanding widely spread statements to the 
contrary, neither zymase nor yeast has any action on starch paste. 

163. Diastasic Action or Diastasis. — The action of diastase, 

being of such great importance in brewing operations, has been studied 
closely. The term " diastase " is occasionally used in a generic sense, 
and is then applied to the hydrolysing agents of the cereals generally ; 
thus cerealin is at times referred to as the "diastase " of bran. Hy- 
drolysis, when effected by diastase or its congeners, is often 
termed diastasic action, for which the shorter term " diastasis" 
is proposed. 

164. Saccharification. — It will be noticed that the ultimate pro- 
ducts of hydrolysis of starch are sugars of various descriptions, hence 
this operation is frequently termed the " saccharification " of starch. 

165. Saccharification of Starch by Acids. — This operation 

is carried on as a commercial process for the manufacture of glucose for 
use in brewing. The starch is boiled, either in open vessels or under 
pressure, with dilute sulphuric acid. If the operation be stopped as 
soon as a portion of the solution gives no blue colouration when tested 
with iodine, it will be found that dextrin and maltose are the chief 
products. Continued boiling results in the transformation of most of 
the dextrin and maltose into glucose. The sulphuric or oxalic acid, 
whichever is used, is next removed by the addition of calcium carbonate 
in slight excess. This reagent forms an insoluble oxalate with the latter 
acid, and with the former, calcium sulphate, which is only very slightly 
soluble. The precipitate is allowed to subside and the supernatant 
liquid evaporated under diminished pressure. 

166. Action of Diastase on Starch.— This reaction may first 

be summed up briefly by stating that if a cold infusion of malt be made, 
and then filtered ; it, the infusion, on being added to a solution of starch 
in water, at temperatures from 15" to about 70° C, more or less rapidly 
hydrolyses the starch into a mixture of dextrin and maltose. The 
longer the operation is continued, the higher is the proportion of maltose 
produced ; but even prolonged action does not result in any further 
hydrolysis of the maltose into glucose. With regard to the history of 
starch and its transformations, there is a paper of singular interest, by 
Brown and Heron, in Vol. XXXV., p. 596, year 1879, of the Chemical 
Society's Journal. Brown, in conjunction with Morris, continues the 
subject in a paper on " The non-crystal] isable products of the action of 
Diastase upon Starch," in Vol. XL VI., p. 527, year 1885, of the same 
journal. 

The following paragraphs (167-173) consist largely of a summary 



TRANSFORMATIONS OF THE CARBOHYDRATES. 77 

of the conclusions arrived at by these chemists as a result of their 
researches. 

Brown, Heron, and Morris' Researches. 

1 67. Malt Extract employed. — It was found that a cold aque- 
ous infusion of malt was the most convenient diastasic agent to employ, 
as diastase when prepared in a pure state was liable to considerable 
variations in activity. With proper precautions, the aqueous infusion 
of malt admitted of any degree of accuracy. The infusion or malt 
extract was prepared by mixing 100 grams of finely ground pale malt 
with 250 c.c. of distilled water. This mixture was well stirred and then 
allowed to stand for from six to twelve hours, and then filtered bright. 
This extract had a specific gravity of 1036-1040. 

168. Action of Malt Extract on Cane Sugar.— Malt ex- 
tract is capable of "inverting" cane sugar, i.e., changing it into glu- 
cose. The term " inverting " is derived from the fact that the resulting 
mixture of glucoses exerts a left-handed rotary action on polarised light, 
while the original sugar is dextro-rotary. The maximum effect is pro- 
duced at about 55° C. ; it is much weaker at 60°, almost destroyed at 
66°, and entirely destroyed by boiling. 

169. Action of Malt Extract on Ungelatinised Starch. 

— Malt extract is incapable of acting on unaltered starch : even when 
contact between the two is maintained for a considerable time, not the 
slightest action is perceptible at ordinary temperatures. 

It is well known that the starch of seeds is attacked and dissolved 
during the natural act of germination, but this action seems to be 
inseparable from the living functions of the vegetable cell. 

This statement is at variance with that of Baranetzky, who avers 
that " the starch granules of different kinds are acted on with unequal 
rapidity by the diastasic ferments of plant juices, the strongest ferment 
of all, malt diastase, being well known to have no perceptible influence, 
even after long exposure, on solid potato-starch granules, while wheat 
and buck-wheat are dissolved with facility." 

Brown and Heron give no particulars as to the action of malt extract 
on ungelatinised starch at higher temperatures; but Lovibond ("Brew- 
ing with Raw Grain,") states that the diffusive action of the diastase 
through the starch cell wall is sufficient, at high temperatures, to effect 
the hydrolysis of the starch granulose. The temperatures at which he 
worked were, however, not much below those given for incipient 
gelatinisation. The author recently made a series of experiments on 
sound wheaten starch, obtained by washing from Hungarian flour ; 
this at 35° C. was not acted on by an infusion of wheat germ. It is 
safe to state that, up to this temperature, sound starch cells are unacted 
on by diastase, whether of malt or the other cereals. 

170. Action of Malt Extract on Bruised Starch.— It 

having been found that sound starch cells resisted the action of malt 
extract, some starch was next triturated in a mortar with powdered glass. 
This treatment results in cutting the cellulose envelopes of the granules. 
The starch granulose is then exposed, and on being treated with malt 



78 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

extract rapidly undergoes conversion. The product consists principally 
of maltose, the actual results obtained in one experiment being that, 
after remaining six hours, the clear solution contained — - 
Maltose, ... ... 86 -3 

Dextrin, ... ... 10.5 

Cellulose, ... ... 3-2 

100-0 
After twenty-four hours in the cold the maltose had suffered a slight 
increase : — • 

Maltose, ... ... 91-4 

Dextrin, ... ... 7'0 

Cellulose, ... ... 1-6 



100-0 
It will be noticed that under these circumstances a small quantity of 
cellulose becomes dissolved. 

171. Action of Malt Extract upon Starch Paste in the 

Cold. — At ordinary temperatures, malt extract acts upon starch paste 
(gelatinised starch) with great rapidity and energy. In 100 c.c. of 
starch solution, containing between 3 and 4 per cent, of solid matter, 
the addition of from 5 to 10 c.c. of the malt extract causes the starch 
to become perfectly limpid in from one to three minutes. Immediately 
after arriving at this point the solution ceases to give a blue colouration 
with iodine. Erythro-dextrin is shown to be present by the brown re- 
action with iodine, and does not disappear within some five or six 
minutes from the commencement of the experiment. In this case also 
a small quantity of starch cellulose is dissolved, but is slowly re-deposited 
on the liquid standing. After remaining three hours, three experiments 
gave a mean of : — 

Maltose, ... ... 80 -4 

Dextrin, ... ... 19 -6 

100-0 
as the composition of the solution, resulting from hydrolysis by malt 
extract. 

172. Action of Malt Extract at higher temperatures.— 

At temperatures of 40° and 50° C, the ultimate products of the action 
of malt extract are found to be practically the same as in the cold, but 
the point of disappearance of erythro-dextrin is reached somewhat less 
rapidly. At 60° C. the action is weakened, but still proceeds sufficiently 
far to produce practically the same amount of maltose At still higher 
temperatures the transformation of the dextrin, first formed, into maltose 
goes on much more slowly. Also, the action of the diastase of the malt 
extract may be weakened by the addition to it of dilute alkalies. Such 
treatment results in limiting the extent to which the conversion of dex- 
trin into maltose proceeds. The results may be summed up by stating 
that, by modifications of the treatment of starch paste with malt ex- 
tract, certain fixed points may be obtained representing several different 
molecular transformations of starch. 



TRANSFORMATIONS OP THE CARBOHYDRATES. 79 

173. Molecular Constitution of Starch, Dextrin, and 

Maltose. — The most natural conclusion that can be derived from these 
varying proportions of dextrin, obtained in modifications of the hydro- 
lysis of starch paste by malt extract, is that there are several dextrins. 
The evidence further points to these dextrins being polymeric, not meta- 
meric bodies (see Chapter III., paragraph 97). This view being adopted, 
Brown and Heron's results led them to the opinion that the simplest 
molecular formula for soluble starch is 10C 12 H 20 O 10 , which may also be 
written C 12xl0 H 20xl0 O 10xl0 . The first change then, produced by the ad- 
dition of malt extract, would be represented by 

^12xiO-"-20xi(Aaoxio + TL 2 = ^12X9-^20X9^10X9 **" ^12"' : '-22^11* 
Soluble Starch. Water. Erythro-dextrin. a Maltose. 

That is, one of the groups of C 12 H 20 O 10 has combined with water to 
form maltose ; the remaining nine groups constitute the first or most 
complex dextrin. By the assimilation of another molecule of water, 
the nine-group dextrin breaks up into a second molecule of maltose and 
an eight-group dextrin. This reaction proceeds through successive 
stages until ^finally the one group dextrin, C^H^O^, is in its turn trans- 
formed into maltose. There are thus theoretically possible nine poly- 
meric modifications of dextrin ; the two higher of these are erythro- 
dextrins ; the remaining seven are achroo-dextrins. The most stable of 
the whole of these dextrins is that resulting from the eighth transforma- 
tion, having the composition C 12X2 H 20X2 O 10x2 : the hydrolysis of starch, 
with the production of this dextrin, would then be represented by 

^12X10-^-20X10^10x10 "f" oH 2 Q = ^i2X2-""20X2^10X2 "*" "^12-"-22^ir 
Solub'e Starch. Achroo-dextrin. £ Maltose. 

In the more recent paper by Brown and Morris, they adduce evidence 
in favour of a third body, malto-dextrin, being formed as an intermediate 
product during the hydrolysis of starch ; as previously mentioned, they 

( C 12 H 22^11 

ascribe to this body the formula, 4 C 12 H 20 O 10 . From this it will be seen 

','... lCl2 H 2oOlO 

that malto-dextrin is composed of a molecule of maltose united with 
two of the one-group dextrin. Viewed in the light of the existence of 
this intermediate product, they now regard the following as the simplest 
molecular formula for starch, capable of accounting for the various re- 
actions observed during its hydrolysis — 

( C 12 H 20^1o)3 

(^12^20^10)3 
j ( C 12 H 20°lo)3 
I ( C 12 H 20°lo)3 
I (^12 H 20^1o)3 

In accordance with this hypothesis, the first step in hydrolysis consists 
in the lesion of one of the ternary groups, which is transformed into 
malto dextrin, by the assimilation of a molecule of water, thus — 

(G K O ^ 4- TT O i ^12-^-22^11 

V^12- n -20 W 1073 + ■ CL 2^ "~ Wo TT A 

I V Vv 12- rL 20 W 10^2 
One of the five ternary groups Water. Malto-dextrin. 

constituting the starch molecule. 



80 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

Malt extract effects the complete conversion of malto-dextrin into 
maltose — 

{(OH 2 o") + 2K *° " 3C i2 H 2 2 0n- 

Maito-dcxtriu. Water. Maltose. 

In the change producing malto-dextrin, the remaining four ternary 
groups of (C 12 H 20 O 10 ) 3 unite to form the most complex of the dextrins. 
As the hydrolysis continues, the remaining ternary groups undergo suc- 
cessively the same change until one only remains : this is identical with 
that before referred to as achroo-dextrin f. The view that the starch 
molecule contains fifteen of the C 12 H 20 O 10 group instead of ten, requires 
that this which may be distinguished as " stable dextrin," shall consist of 
three groups of C 12 H 20 O 10 instead of two : this, of course, make the 
formula the same as that of one of the ternary groups. The reaction 
for the production of stable dextrin is then represented by the following 
equation : — 

( C 12 H 20°lo)3 

(C 12 H 20 O 10 ) 3 J C 12 H 20 O 10 

(Ci2H 20 O 10 ) 3 + 12H 2 = i C 12 H 20 O 10 + 12 C 12 H 22 O n . 

(^12 H 20°lo)3 1^12 H 20^10 

> ( C 12 H 20 lo)3 
Soluble Starch. Water. Stable Dextrin. Maltose. 

Such, very briefly summarised, are the opinions advanced by Brown, 
Heron, and Morris, as to the relative molecular constitutions of starch, 
dextrin, and maltose. 

Details of Hydrolysis. 

174. Empirical Statement of Hydrolysis of Starch. It 

will be seen that these formulae, representing the probable constitution 
of the molecule, are much more complex than the empirical formulae 
respectively of starch and dextrin. The following empirical equation 
represents in the simplest possible manner the above reaction ; it must 
not, however, be viewed as representing the true nature of the mole- 
cular change involved : — 

(C„H 10 O 5 ) 5 + 2H 2 = C 6 H 10 O 5 + 2C 12 H 2a O u . 

Soluble Starch. Water. Dextrin. Maltose. 

175. Hydrolysis of Cane Sugar. — This operation is slowly 

effected by the action of malt extract, or even by prolonged boiling 
with water, which effects the same change more or less completely. At 
ordinary temperatures, dilute sulphuric and hydrochloric acids are capable 
of slowly inverting cane sugar ; at temperatures of from 65° to 70° C. the 
hydrolysis occurs with extreme rapidity. Zymase also slowly hydrolyses 
this compound. For laboratory purposes, complete inversion is effected 
by adding to the moderately strong sugar solution one-tenth its volume 
of strong hydrochloric acid, and then heating the mixture in a water- 
bath until the temperature reaches about 68° C. The change consists 
of the cane sugar molecule splitting up into two molecules of glucose, the 
one being dextro-, and the other lcevo-rotary — 

C 12 H 22 O 10 + H 2 = C 6 H 12 6 + 6 H la O 6 . 

Cane Sugar. Water. Dextro-glucoMe. Lcevu-glucose. 



TRANSFORMATIONS OF THE CARBOHYDRATES. 81 

176. Hydrolysis Of Dextrin. — By the action of acids, and also 
of malt extract, this body may be entirely converted into maltose : the 
nature of the chemical change has been described when treating of the 
hydrolysis of starch. Under ordinary conditions, neither zymase nor 
yeast itself is capable of effecting the hydrolysis of dextrin. 

177. Hydrolysis Of MaltO-dextrin. — This change is readily 
effected by the action of malt extract, but not by either zymase or 
yeast. 

178. Hydrolysis Of Maltose. — Maltose is a more stable sugar 
than is cane sugar : dilute acids effect its conversion with slowness ; 
thus a maltose solution may be boiled for some minutes with dilute 
sulphuric acid without undergoing change. Complete inversion results 
from keeping the solution at a temperature of 100° C. for some six or 
eight hours. The principal product of inversion is probably either 
dextrose, or one or more closely allied dextro-glucoses. As has been 
previously stated, malt extract has no hydrolysing action on maltose. 
Zymase converts maltose into glucose. The probable chemical change 
is — 

Ci2 H 22°n + H 2° = 2 C 6 H 12 6 . 

Maltose. Water. Dextro-glucose. 

179. Saccharification of Malt during the Mashing 

Process. — This process is of interest, both from the technical point of 
view, as being largely used by the baker, and also scientifically, as 
representing an important example of hydrolysis by malt extract. Malt 
contains the active hydrolysing principle, diastase, and also from 55 to 
60 per cent, of starch. In the operation of malting, the walls of the 
starch granules get more or less ruptured and fissured ; hence the 
interior granulose is at the outset somewhat exposed to the action of 
the diastase. As a first step toward the preparation of beer, the brewer 
treats his ground malt with water at a temperature of from 65*5° C. 
(150° F.) to 71-1° C. (160° F.) This results in the conversion of the 
starch present into dextrin and maltose. This operation he terms 
" mashing." The first change is that the starch becomes gelatinised, 
and is then freely susceptible to the action of diastase. At temperatures 
below the gelatinising point of starch, diastasis can only proceed in the 
case of such starch cells whose walls are fissured. At a temperature of 
about 60° C. (140° F.) almost all the starch and also the erythro-dextrins 
will have disappeared in about twenty minutes ; this point may be 
ascertained by taking out a drop of the liquid and testing it with iodine. 
An increase of temperature weakens the action of the diastase ; hence 
a mashing made at 60° C. (140° F.) yields in two hours, for the same malt, 
about 7 per cent more dextrin and maltose than when mashed at 76*6° C. 
(170° F.). Further, as might be expected from the results already 
mentioned, the proportion of dextrin is much greater in the mashing 
made at 76 '6° C. than at 60° C. The duration of the mashing operation 
has also an influence on the amount of dextrin and maltose produced. 
With a temperature of 62*7° C. (145° F.) most of the starch is converted 
into dextrin and maltose within thirty minutes, but for some time after, 
the yield of these continues to slightly increase. The proportion of 



82 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



maltose to 


dextrin also becomes higher with a longer mashing. The 


following is 


the result of an 


experiment by 


Graham :— - 


Length of 
Mashing. 


Percentage of 
Maltose. 


Percentage of 
Dextrin. 


Total percentage 

of Ratio of Maltose 
Maltose & Dextrin. to Dextrin. 


\ hour. 


48-60 


14-61 


63-21 3-3 : 1 


1 „ 


52-35 


12-26 


64-61 4-2 : 1 


2 hours 


53-56 


11-39 


64-95 4-7 : 1 


3 „ 


54-60 


11-05 


64-65 4-9 : 1 


7 „ 


61-47 


3-53 


65-00 17-4 : 1 



It will be seen that by far the greatest proportion of the transfor- 
mation is effected within the half hour, while for all practical purposes 
the hydrolysis is completed within two hours at the furthest. 

180. Mashing Malt together with Unmalted Grain.— The 

diastase of good malt is not merely capable of saccharifying its own 
starch, but is competent also to hydrolyse in addition considerable 
quantities of starch from other sources ; hence, in brewing operations, 
malt is frequently mixed with flour from other cereals, either rice or 
maize being commonly chosen. The diastase of the malt saccharifies 
the whole of the starch present ; but with the proportion of malt unduly 
low, the ratio of maltose to dextrin produced is comparatively small. 

181. Conditions Inimical to Diastasis. — Diastasic action is 

rapidly weakened at temperatures above 65° C. ; while at 80-81° the 
•diastasic power of malt extract is entirely destroyed. Acetic and 
hydrocyanic acids, strychnine, quinine, and the salts of these bases very 
slightly retard the action of diastase Alkaline carbonates, dilute 
caustic alkalies, ammonia, arsenious acid, and magnesia exercise a some- 
what greater retarding influence, depending on the amount of these 
bodies added. The following bodies completely prevent the action of 
diastase upon starch— nitric, sulphuric, phosphoric, hydrochloric, oxalic, 
tartaric, citric, and salicylic acids ; caustic potash, soda, and lime ; 
copper sulphate and acetate ; mercury chloride, silver nitrate, iron per- 
sulphate, alum, and borax. On the other hand — alcohol, ether, 
choloroform, creosote, essence of turpentine, cloves, lemon, mustard, 
<fec, exert no retarding influence. 

Experimental Work. 

182. Hydrolysis Of Starch. — Mix 10 grams of starch with 
200 c.c. of water, and gelatinise by placing in the hot water-bath. Take 
50 c.c. of this solution and add to them 10 c.c. of five per cent, sul- 
phuric acid Maintain at a temperature of 100° C. until a few drops 
taken out with a glass rod or tube, and placed on a porcelain tile, give 
no blue colouration on addition of iodine. To the solution, add preci- 
pitated calcium carbonate, or powdered marble, until it ceases to pro- 
duce effervescence. Allow the precipitate to subside, and filter : taste 
the clear solution, notice its sweetness. Test a portion of this filtered 
solution with Fehling's solution, a red precipitate is produced, showing 
that either maltose or glucose is present. 

To a test tube, containing another portion of the original starch solu- 
tion, add some saliva, and stand it in a water-bath at a temperature of 



TRANSFORMATIONS OF THE CARBOHYDRATES. 83 

about 40° C. for some time : notice that the solution becomes more limpid, 
and ultimately that it gives no starch reaction, on a few drops being 
taken out and treated with iodine. Test now for maltose, by means of 
Fehling's solution; a red precipitate is produced. As a complement to 
this experiment, boil some corn-flour and water, allow the paste to cool, 
place a spoonful in the mouth, retaining it there for some fifty or sixty 
seconds, and mixing it with saliva by means of the tongue : notice that 
the paste becomes limpid, and acquires a sweet taste. 

Take some fresh compressed yeast, mix a little with some of the starch 
solution and place in the water-bath at 40° C. Notice that after several 
hours the starch remains unaltered, giving a blue colouration with 
iodine, and little or no reaction with Fehling's solution. Prepare some 
" yeast-water " by shaking up about 50 grams of the compressed yeast 
with 150 c.c. of cold water; let this stand for from four to six hours, 
shaking occasionally, then allow to subside and filter the supernatant 
liquid. Treat some starch solution with this yeast-water in the same 
way as with the yeast itself: notice that this also causes no alteration 
in the starch. 

Make an aqueous extract of malt, as described in paragraph 167. 
Take some sound wheat starch, examine it under the microscope, to see 
that none of the granules are fissured or cracked. Add some of the 
malt extract to a portion of this starch and allow it to remain for some 
hours at a temperature of 20° C Maintain another similarly prepared 
sample at a temperature of 40° C. for from six to twelve hours. At in- 
tervals, from the time of starting the experiment, and at the end of the 
time, examine the starch in each case carefully under the microscope, 
in order to see whether any of the granules show signs of cracking or 
pitting. Make a comparative series of experiments on potato starch. 
In every experiment, at the end test the starch granules with iodine, in 
order to see whether they still give the starch reaction. 

Shake up some starch with water, and filter : notice that the clear 
filtrate gives no reaction with iodine. Rub a little of the starch in a 
mortar, with powdered glass ; this cuts the cellulose envelopes. Shake 
up with water, and filter ; to the clear filtrate add iodine solution, a blue 
colouration shows the presence of soluble starch. To some of the bruised 
starch add malt extract, and allow to stand for twenty-four hours at 20° 
or 25° C, examine under the microscope, and notice that much of the 
interior of the cells is dissolved away. Treat a little with iodine, and 
examine under the microscope in order to determine how much unaltered 
starch remains. Make some starch paste as described in paragraph 
171 ; treat it with malt extract as there mentioned, and at intervals of 
a minute take out a drop of the solution, by means of a glass rod, and 
test with iodine on a porcelain tile. Note the time when the starch 
and the erythro-dextrins disappear. Make a series of similar experi- 
ments with varying temperatures, rising by 10° C. at a time from 15° C. 
to the point at which diastasis ceases. The quantities of solution should 
be measured ; and in each case, both the starch and the malt extract 
solutions should be allowed to stand in the water-bath, regulated to the 
desired temperature, until both have acquired that temperature, then 
mix the two and note the time. If desired, the bath may be regulated 



84 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

for this experiment by means of the regulator, described and figured in 
Chapter XI. ; in that case it is not absolutely necessary to get the 
temperature nearer than a degree, but the exact temperature, as read 
by a thermometer, should be noted. 

Make a cold aqueous infusion of bran or pollard in the same way as 
described for malt, and treat starch solution with it, as was done with 
the malt extract, both in the cold and at higher temperatures. If 
separated wheat germ is obtainable, make a similar series of experiments 
with that substance. 

183. Hydrolysis of Cane Sugar. — Mix cane sugar solution 

with strong hydrochloric acid, and heat to 68° or 70° C, as described in 
paragraph 175. After hydrolysis, test for reducing sugars by Fehling's 
solution. To another portion of the cane sugar solution add some 
yeast-water, and maintain for three or four hours at 40° C, after which 
test for maltose or glucose by means of Fehling's solution. 

184. Mashing Of Malt. — Take 100 grams of ground malt, and 
mix with 500 c.c. of water at 60° C. in a large beaker : weigh the 
beaker and its contents, and place it in a water-bath at 60° C. Stir 
occasionally, and from time to time take out small quantities of the well- 
stirred liquid, and test for starch by iodine solution. Note how long it 
is before the starch disappears ; as soon as iodine produces no blue 
reaction, wipe the outside of the beaker, place it in the balance, and add 
distilled water until that lost by evaporation has been replaced : when 
this point is reached the beaker weighs just the same as before being 
placed in the bath. Then filter the clear solution, cool rapidly to 1 5° C. , 
and take the density by means of a hydrometer. The method of using 
the hydrometer, and the conclusions to be drawn from the density of 
the wort are described in the paragraph on " Specific Gravity of Worts," 
in Chapter XII. Make similar mashings at the temperatures respectively 
of 50° and 70° C. : note in each case the time requisite for saccharifi- 
cation, and the density of the wort. For the different experiments both 
the mashing liquor and the bath must be regulated to the temperature 
desired. 

185. Substances mimical to Diastasis. — Prepare some 

starch solution and malt extract as in paragraph 182. To a portion of 
the malt extract add a small quantity of caustic potash, and note the 
time it takes to saccharify the starch, both starch and malt being used 
in the same proportions as before. Make similar tests with solutions of 
sulphuric, tartaric, and salicylic acids ; lime, copper sulphate, alum, 
borax, alcohol, and essence of turpentine. 



ALBUMINOIDS OR PROTEIDS. 



85 



CHAPTER VIII. 



ALBUMINOIDS OR PROTEIDS. 



186. The most important nitrogenous substances present in wheat 
and flour are those classified together as albuminoids or proteids. These 
are substances of extremely complex constitution, and have very high 
molecular weights. They are non-crystallisable and highly colloid bodies. 
The albuminoids consist of a number of more or less allied compounds, 



derived from both the animal and 



vegetable 



kingdom : they are so 



named because of their similarity in composition and general properties 
to the white of egg, which may be taken as a type of the others. It is 
in some cases doubtful whether the albuminoids from different sources 
are or are not identical with each other, while in other instances, their 
physical characters indicate that they are distinct bodies. 

187- List of Albuminoids. — The following is a list of the more 
important compounds commonly classed as albuminoids — 

I. Albumin of the egg, albumin of serum (the liquid portion of co- 
agulated blood), vegetable albumin. 
Casein, vegetable casein, or legumin. 

Blood fibrin, vegetable fibrin, or insoluble albumin, gliadin or 
glutin, and mucin or mucedin. 
IV. Diastase, and cerealin. 

188. Composition Of Albuminoids.— In percentage composi- 
tion, the albuminoids closely resemble each other ; but still there are 
sufficient differences to render it improbable that they are simply iso- 
meric or polymeric bodies. In the following table, the results of analyses 
of some of the more important of these bodies are given — 



II. 
III. 





Egg Albumin. 


Blood 
Fibrin. 


Casein. 


Gluten. 


Legumin. 


Not Co- 
agulated. 


Purified. 


Co- 
agulated. 


Carbon, 


53-3 

7-1 

15-8 

22-1 

1-8 


52-9 

7-2 

15-6 


52-9 

7-2 
15-8 


52-8 

7-0 

16-8 

23-4 


53-5 

7-1 

15-8 

23-6 


53-1 

6-8 

15-0 


53-7 

7-2 
15-7 

234 


Hydrogen, 

Nitrogen, 

Oxygen and I 
Sulphur, J 
Sulphur, 



It will be seen that in composition they are very similar, but also 
that differences exist, greater than can be accounted for by experimental 



86 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

errors in analysis. One obstacle in the way of arriving at accurate 
knowledge of the composition of the albuminoids is that their prepara- 
tion in a state of purity is a matter of difficulty. The albuminoids con- 
tain, in addition to carbon, hydrogen, and oxygen, not only nitrogen, 
but also sulphur. It was at one time conjectured that this latter ele- 
ment was simply an accidental ingredient of albumin ; further research 
has led to its being recognised as an essential constituent of the albumi- 
noids. From the above quoted percentage composition of egg albumin, 
Lieberkiihn has calculated that its simplest possible empirical formula 
is CL 2 H 112 Nj 8 22 S. This being the empirical formula, it is highly pro- 
bable that the actual molecule may contain several such groups. Fur- 
ther, if certain of the albuminoids are polymeric, their formulae will 
consist of different multiples of this group. 

189. Egg Albumin. — It was not long after the attention of 
chemists had been turned to the study of flour that it was found that 
on washing a lump of dough, enclosed in muslin, in water, an elastic 
body remained. It was further observed that, on being burned, this 
peculiar substance evolved an odour similar to that given off by many 
animal substances under the same circumstances. Among these bodies 
there was one in particular which, as more exact investigation was 
made, was found to possess a most remarkable resemblance to this 
elastic constituent of flour. The body referred to is the white of an 
egg, and, as the type of the bodies whose chemistry is now being studied, 
merits a somewhat extended description. It is frequently stated that 
white of egg is an almost pure form of " albumin," that being the name 
of the compound whose presence confers on this substance its character- 
istic properties. Albumin is not, however, the principal constituent of 
the white of egg, as it only amounts to about 1 2 per cent, of the whole 
mass, the remainder being water. Not only is albumin found in eggs, 
but also in blood serum and most of the organs of the body. Albumin 
exists in two distinct modifications, viz., in the soluble and liquid form, 
and also in an insoluble form, which may be produced from the soluble 
by the action of heat. The two forms are identical in chemical com- 
position : instances of the both occur in respectively the raw and the 
boiled white of egg. The albumin, both of blood serum and white of egg, 
on being burned, leaves behind a residue consisting principally of sodium 
carbonate. This leads us to consider that these bodies really contain 
albumin in a state of combination, with sodium as a base, and that 
albumin itself may be viewed as a weak organic acid. In its purest 
form albumin has a slightly acid reaction with litmus. 

Pure albumin may be obtained from white of egg by first beating it 
up with water ; this treatment breaks the cell walls and liberates the 
soluble compound of albumin and sodium. In order to effect the separa- 
tion of sodium and albumin, a lead salt (the sub acetate) is added ; this 
produces a precipitate of lead albuminate. This precipitate is thoroughly 
washed and then made into a paste with water, the lead is then re- 
moved by passing carbon dioxide gas into the liquid ; lead carbonate is 
precipitated, and albumin remains in solution. The solution, on being 
evaporated at low temperatures, yields a residue of pure soluble albumin. 
Albumin thus obtained is a pale yellowish, translucent mass, which may 



ALBUMINOIDS OR PROTEIDS. 87 

be easily powdered. It swells when treated with pure water, but does 
not dissolve freely ; the addition of any alkaline salt causes its ready 
solution. Albumin prepared in this manner leaves no appreciable 
residue on being burned. On analysis it is found to possess the 
following percentage composition : — Carbon, 53*3 ; hydrogen, 7*1 ; nitro- 
gen, 15*7 ; oxygen, 22*1 ; and sulphur, 1*8. A solution of albumin in 
water,. on being heated, becomes opalescent at a temperature of 60° C. 
(140° F.), and at 63-3— 87-7° C, (146—190° F.), the whole coagulates 
in a mass. When the liquid is very dilute it simply becomes turbid, 
and deposits " flocks " of albumin on evaporation. Albumin is insoluble 
in alcohol and ether ; these bodies, on being added in excess to the 
aqueous solution, precipitate albumin in the coagulated form. Oils and 
fats, whether fixed or volatile, are without action on albumin. Nearly 
all the acids precipitate albumin from its solution ; so also does mercuric 
chloride and other salts ; nitric and picric acids are in this way specially 
effective, and are frequently used as tests for the presence of soluble 
albumin. 

If a small quantity of acetic acid be added to the white of egg, so as 
to just neutralise the alkali ; and then the liquid diluted with water, 
flocks of albumin are after a while deposited. This precipitate im- 
mediately dissolves on being treated with a small quantity of nitre or 
common salt : the solution thus obtained is coagulated on boiling. 

A solution of albumin exerts a loevo-rotary action on polarised light : 
it has no reducing action on Fehling's solution. 

On boiling coagulated albumin with water for about sixty hours it 
gradually disappears, being converted into a substance soluble in water. 
The white of egg, when boiled, gives up a portion of its sulphur as 
sulphuretted hydrogen. Soluble albumin, or the white of egg, on being 
allowed to stand, putrefies, with the evolution of sulphuretted hydrogen 
and other gases. The odour of sulphuretted hydrogen is almost in- 
variably described by comparison to that of rotten eggs. 

Coagulated albumin, when dry, is a fairly stable body ; but, when left 
in contact with water, putrefies, yielding valeric and butyric acids, 
together with other bodies. The oxygen of the air has no action on 
albumin. 

190. Blood Albumin. — This body, from a chemical point of view, 
behaves almost exactly similarly to egg albumin. 

191. Vegetable Albumin. — Not only is albumin found in different 
animal products, as white of egg, but is also a constituent of most 
vegetable juices ; for instance, on making a cold aqueous infusion of 
flour, or, still better, of the germ of wheat, and then filtering the solution 
until properly clear, a liquid is obtained which, on being raised to the 
boiling point, throws down abundant flocks of albumin. The albumin, 
thus precipitated, is as white and pure in apearance as that from the 
white of egg, and is, to all intents and purposes, identical with that of 
egg, and blood serum. While the egg albumin always occurs in an 
alkaline liquid, that of vegetables is always found either in acid or 
neutral liquids. 

192. Legumin or Vegetable Casein. — After the removal, by 



88 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

boiling, of vegetable albumin from an aqueous extract of flour, there 
still remains another albuminoid body in solution ; the albumin having 
been filtered off, an addition of acetic acid produces a further precipitate 
of a compound known as "legumin," or vegetable casein. Peas, beans, 
and lentils are the principal sources of legumin, these bodies being 
frequently termed leguminous bodies. A solution of legumin is not 
coagulated by boiling, but on evaporation is covered with a film or 
pellicle similar to that which forms on milk on being heated. Legumin 
in many respects resembles the casein or nitrogenous matter of milk. 
Legumin, on putrefying, acquires properties very similar to those of the 
other wheat albuminoids. 

193. Soluble Albuminoids Of Wheat.— These consist prin- 
cipally of vegetable albumin and legumin ; they are not distributed 
equally throughout the whole seed, there being certain portions of the 
wheat grain which are specially rich in soluble albuminoids ; the bran 
and germ are particularly so. Starting from the outside of the seed, 
the interior portions become less and less nitrogenous, until the kernel 
of the grain is found to consist almost entirely of starch. Bran, on 
being treated with dilute alcohol, in order to remove dextrin and maltose, 
and then with water, yields to the latter solvent an albuminoid body 
which may be coagulated by the action of heat. The aqueous infusion 
of germ, as has been already stated, also throws down an abundance of 
an albuminoid body on being heated ; this albuminoid is very similar 
to that of the bran. They both possess points of very great interest to 
the miller and baker. 

194. Insoluble Albuminoids of Wheat, Gluten.— Every 

miller and baker knows that flour, on being moistened, forms a stiff, 
tenacious paste or dough ; he further knows that the flour of wheat is 
distinguished in a remarkable manner from other flours by this char- 
acter; for oatmeal, when similarly treated, simply produces a damp mass, 
having little or no tenacity. On kneading a mass of wheaten dough, 
enclosed within a piece of muslin, with water, until the starch is sepa- 
rated, there remains behind a greyish white sticky elastic mass, to which 
the name of " crude gluten " is applied. This substance consists of the 
insoluble albuminoids of the wheat, together with a portion of the ash, 
and also of the oily matter. Although this gluten, when in the flour, 
existed as a powder, yet, on the addition of water, it thus swells up into 
a tough mass. Gluten is practically insoluble in water, and without 
taste ; on being dried by exposure to the heat of the hot-water oven, it 
changes into a hard, horny mass. Gluten which has been thus moistened 
with water, and dried, does not again swell up on being wetted. The 
dry gluten may be kept for a long time without change, but if when 
wet it is exposed to air at ordinary temperatures it gives of a quantity 
of gas, and at last evolves a strong putrescent odour. At the same 
time, the insoluble gluten breaks down into a thick creamy mass. Gluten 
is not a simple chemical compound, but may be split up into distinct 
proximate principles. 

1 95. Composition Of Gluten. — According to Ritthausen, gluten 
consists of three separate albuminoids, termed respectively — glutin, 



ALBUMINOIDS OR PROTEIDS. 89 

gliadin or vegetable gelatin, mucin or mucedin, and vegetable fibrin. 
To effect the separation of these bodies, freshly washed gluten must be 
cut up into small fragments and digested for several hours with alcohol 
of 80 or 85 per cent, strength. The alcohol is then raised to the boiling 
point, and maintained at that temperature for half-an-hour. The 
supernatant liquid is then poured off and filtered, and the residual mass 
of gluten heated several times with alcohol of 75 per cent. The mixed 
alcoholic filtrates become turbid if allowed to cool ; but on their being 
subjected to distillation until half the alcohol has been expelled, the 
remainder, on cooling, deposits considerable quantities of flocculent 
mucin, together with glutin and fat. In order to purify the mucin, 
it is dissolved in 50 per cent alcohol ; the solution is filtered, while hot, 
through fine calico, and then allowed to cool, being frequently agitated 
while the deposit, consisting of mucin, forms. The whole of the glutin 
is then contained in the clear liquid, together with traces of mucin. In 
order to obtain the glutin from the clear liquid, it is evaporated over 
the water-bath, this renders any mucin present insoluble ; the glutin 
may then be redissolved in alcohol or dilute acetic acid, and filtered 
from the mucin. The portion of the gluten which remained insoluble, 
when digested and finally boiled with alcohol, consists of vegetable 
fibrin. 

Giinsberg is of opinion that Ritthausen's mucin is not a separate 
chemical compound, but simply fragments of suspended fibrin j he 
further considers that the gliadin obtained by Ritthausen's method is 
not a simple proximate principle, for cold water extracts from it a brown 
substance, containing nitrogen and sulphur. The residue, on treatment 
with boiling water, is dissolved, and on cooling deposits a sulphur free 
substance, containing carbon, 52 '77 ; hydrogen, 6*79 ; nitrogen, 17*66; 
and oxygen, 22*78 per cent. Giinsberg regards this substance as being 
true vegetable gelatin : it has nearly the same composition as animal 
gelatin. Ritthausen's views are, however, those most commonly held. 

196. Glutin, Gliadin, or Vegetable Gelatin. — This body, 

when in the hydrated state, is either a yellowish limpid liquid, or with 
a less proportion of water, a soft pasty substance, capable of being 
drawn out into threads. On the water being removed by alcohol, and 
subsequent treatment with ether; glutin, on being dried in vacuo, forms 
a brittle mass. Alcohol of from 40 to 80 per cent, dissolves glutin 
readily, but absolute alcohol precipitates it from solutions ; on evapora- 
tion of alcoholic solutions, glutin separates in a form exactly resembling 
animal gelatin. Glutin dissolves slightly in cold, and somewhat more 
readily in hot water ; consequently, prolonged washing of wet gluten 
slowly removes the glutin. Glutin is precipitated from its solutions by 
mercuric chloride, and is dissolved easily and completely by tartaric, 
acetic, and other organic acids. Moist glutin is stained a fine red 
colour by mercurous nitrate. As a result of the action of heat, glutin 
becomes changed into forms much less soluble both in water and in 
alcohol. Gliadin, left in contact with water, passes into solution and 
putrefies. 

Pure glutin yields, on analysis, carbon, 52.49 ; hydrogen, 6*97 ; nitro- 
gen, 18-02 ; sulphur, 0*85 ; oxygen, 21*41 ; ash, 0*26 per cent. 



90 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

Glutin is that constituent of wheaten flour which imparts to it the 
property of forming a stiff elastic dough, capable of retaining vesicles of 
gas, and thus producing a light and porous loaf. The flours of barley, 
rye, and oats, yield only traces of glutin on being boiled with alcohol : 
their insoluble albuminoids consist of only vegetable fibrin. Glutin is 
also absent in sensible quantity from the flours of peas, beans, and len- 
tils. Glutin occurs in the juice of the grape. 

197. Mucin, or Mucedin.— Mucin, when prepared according to 
the preceding directions, is a transparent slightly coloured flocculent 
body. On removal of water by absolute alcohol, and then drying in 
vacuo, mucin acquires a greyish-white colour, and becomes brittle. 

Mucin dissolves in boiling alcohol, and separates out on cooling ; cold 
acetic acid also dissolves it. Under certain circumstances, this body 
assumes an insoluble form, when it is scarcely distinguishable from fibrin. 
This change may be produced by leaving the precipitated mucin for 
some time in contact with cold water, or in dilute alcohol. 

198. Vegetable Fibrin, or Insoluble Albumin. — This body 

constitutes about 80 per cent, of the crude gluten, and consists of that 
portion of the albuminous matter of flour, insoluble in water and alcohol. 
Vegetable fibrin occurs also in rye, barley, and the other cereals. Vege- 
table fibrin, when prepared according to Pitthausen's directions, before 
given, is a greyish-white elastic mass, still containing small quantities 
of starch. From these it may be purified by solution in dilute caustic 
potash, and filtering the liquid. Acetic acid is then added in sufficient 
quantity to neutralise the potash, when the fibrin is re-precipitated. 
Any traces of fat present may be removed by exhaustion with ether. 
Vegetable fibrin on being dried, forms a brownish horny mass, which 
slowly recovers its original condition when left in contact with water. 
It is dissolved by acetic, hydrochloric, and phosphoric acids, caustic 
potash and soda, and ammonia ; it may be re-precipitated from any of 
these solutions by neutralisation with either dilute alkali or acid. Com- 
mon salt (sodium chloride) precipitates vegetable fibrin from its solu- 
tions, and retards or arrests the action on it of dilute acids as solvents. 
Diastase exercises a solvent action on vegetable fibrin. 

Vegetable fibrin, being insoluble in water, cannot properly be said to 
be capable of forming an insoluble modification ; but such fibrin is some- 
times found to hydrate during the doughing of flour much more slowly 
than at others. 

199. Mutual Relations of Glutin, Mucin, and Vegetable 

Fibrin. — It will be seen that these three bodies, gliadin, mucin, and 
vegetable fibrin are similar in composition, and differ principally in their 
relative solubility. The difference in character between the glutens of 
various wheats depends, in part at least, on the relative proportions in 
which these three bodies are present, and also on whether they exist in 
the soluble or insoluble forms. 

200. Non-existence of Gluten as such in Flour. — The 

view is in some quarters held that gluten as such does not exist in 
flour, but is formed when the flour is wetted, from the previously exist- 
ing; nitrogenous bodies. If wheaten flour be moistened with alcohol of 



ALBUMINOIDS OR PROTEIDS. 91 

only moderate strength, dough is not formed, but simply a damp, sandy 
mass, similar to moistened oat flour ; the same effect is produced when a 
strong solution of salt is used instead of water. 

While diastase is capable of transforming starch into dextrin and 
maltose, it is advocated by some that a body exists which hydrolyses 
the dry nitrogenous constituents of wheat into the moist tenacious 
gluten. It is well known that certain chemical changes are produced 
on moistening vegetable substances ; thus bitter almonds, on being crushed 
with water, yield hydrocyanic (prussic) acid and bitter almond oil, 
which bodies were certainly not present previous to the treatment with 
water. So, too, mustard only possesses its irritating properties after 
being moistened : there is not a trace of the pungent mustard oil in the 
dry seed, but this body is formed by a special diastase on the addition of 
water. 

The view referred to is, that gluten is also produced through the 
agency of a special diastase, and by hydrolysis of bodies before in the 
flour. In accordance with this supposition, flour, as such, contains an 
albuminous body termed " vegetable myosin," and this compound, by 
hydrolysis, through the action of a special diastase, is changed on mois- 
tening the flour into glutin. Myosin is a substance extracted from 
clotted muscle, and exhibits the usual reactions of albuminous sub- 
stances. It is insoluble in water, alcohol, and ether, and is exceedingly 
soluble in dilute alkalies and very dilute acids, also in solutions of neu- 
tral salts. It is especially soluble in a 10 per cent, solution of sodium 
chloride. Vegetable myosin is the name given to a somewhat similar 
substance extracted from vegetable sources. Weyl and Bischoff treated 
flour with a 15 per cent, sodium chloride solution in order to remove 
the myosin ; they then found that the residue formed no gluten, and 
conclude that the myosin is the gluten forming compound. They also 
state that flour, as a result of being heated for several hours to 60° C. 
loses the faculty of forming gluten ; in this case they were of opinion 
that the non-formation of gluten was not due to the absence of a dias- 
tase, but to the coagulation of the albuminoid matter. This particular 
diastase has not as yet been isolated. According to this diastase hy- 
pothesis, those flours which hydrate slowly on the addition of water are 
deficient in this gluten-forming diastase. The existence of this body 
cannot as yet, however, be recognised as proved. While the formation 
of gluten may be due to the intervention of such a body, yet there is 
nothing remarkable in considering it to be a simple and direct hydration, 
by water, of the gluten compounds existent in the grain. The effect of 
heating the flour, and of treatment with salt solution, are fairly accounted 
for by their well-known coagulating action on the albuminous matters. 
So, too, those wheats whose flours hydrate slowly are grown under condi- 
tions which favour the albuminoids being in a difficultly soluble condition. 

201. Oerealin.— Soluble albuminoids in considerable quantities are 
obtained from the bran and germ of wheat ; these exert an action 
similar to that of diastase on starch paste, and have been assumed to 
contain a distinct proximate principle. That view will probably have 
to be limited to the sense in which diastase is considered a distinct 
substance. 



92 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

202. Putrefaction and its relation to Diastasis.— One 

particular property possessed by the albuminoids is, that in the presence 
of moisture they speedily putrefy, or, in other words, become rotten. 
It is necessary to get accurate ideas of what putrefaction really is. 
Every one knows the results of putrefaction in their last or extreme 
stages ; animal and vegetable substances both give off gases having 
most disgusting odours, and yield a variety of offensive products. 
These gases consist of compounds of hydrogen with carbon, and also 
with sulphur; this latter gas, termed by the chemist sulphuretted 
hydrogen, is, as before stated, responsible for the odour so characteristic 
of rotten eggs. In the earlier stages, however, of putrefaction, the 
changes do not result in the production of such disagreeable bodies ; 
gases are evolved, but these are either inodorous or at most possess only 
slight smells. Speaking broadly, putrefaction consists of the breaking 
down or degrading of the complex molecules of animal and vegetable 
structures into compounds of a more simple character, and ultimately 
into inorganic compounds, such as carbon dioxide, water, and sulphuretted 
hydrogen ; which latter, in its turn, deposits its sulphur, and forms water 
by the action of atmospheric oxygen. Bodies in the first stage of 
putrefying absorb more or less oxygen ; when this element has been re- 
moved from the supernatant air, a species of fermentation, known as 
putrefactive fermentation proceeds. When dealing with the whole 
question of fermentation this change must be viewed more closely. At 
present there is one particular point that should, however, be mentioned, 
and that is, that by heating any organic liquid, as a solution of hay, 
white of egg, or albuminoids of flour, under pressure at a temperature 
of about 266° F. for some time, and then boiling the liquid in a flask 
whose neck is loosely plugged with cotton wool until the whole of the 
air is expelled, the liquid acquires the property of resisting putrefactive 
action. Solutions preserved in this manner may be kept for an in- 
definite length of time ; on being once more exposed to the air they 
again are subject to putrefaction. It would thus appear that putre- 
faction is not a process appertaining exclusively to the grain itself, but 
is in some way dependent on the action and presence of air. The 
soluble albuminoids of the different parts of the wheat grain, and also 
those produced by gluten during its first stages of decay, exercise a 
more or less decided diastasic action on starch paste, or even on starch 
granulose, when exposed by rupturing the outer cellulose envelope of 
the starch granules. Cerealin, the albuminoids of the germ, and also 
those produced by the incipient decomposition of gluten, are in many 
respects very similar to diastase. 

203. Diastase. — It has already been found necessary to mention 
this body, and to describe its action on starch paste. It will now be 
requisite to give some further views as to its nature and composition. 
Diastase is a soluble albuminoid body, and can be prepared in a state of 
considerable purity from malt, by precipitating a cold aqueous infusion 
with alcohol, repeatedly washing the precipitate with the same reagent, 
and finally drying in vacuo. Prepared in this manner, diastase is a 
white, amorphous, easily soluble powder, retaining its activity for a con- 
siderable time. The proportion of diastase in malt does not exceed 0*002 






ALBUMINOIDS OR PROTEIDS. 93 

to 0*003 per cent. One part of well-prepared diastase is stated to suffice 
for the conversion of 2000 parts of starch. A solution of diastase is ex- 
ceedingly unstable, rapidly becoming acid, and losing the power of diastasis. 

Referring again to Brown and Heron's valuable paper, these chemists 
find that, on heating malt extract to a temperature of about 46° C, the 
soluble albuminoids commence to coagulate ; a continuance of this tem- 
perature for some 15 to 20 minutes effects the maximum amount of 
coagulation possible at 46° C. On raising the temperature a few degrees, 
an additional quantity of albuminoids coagulate ; this further increase 
of coagulation continues, as the temperature rises, up to about 95° C. 
The albuminoids of malt extract may be viewed as being composed of 
distinct fractions, each of which has a definite coagulating point, varying 
from 46° to 95° C. With the coagulation of the albuminoids, the diastasic 
power of the malt extract diminishes ; also, no diminution of starch con- 
verting power has been observed without a coagulation of albuminoids. 
Further, at the point at which the diastasic power of malt extract is 
destroyed, (80-81° C), nearly the whole of the coagulable albuminoids have 
been precipitated. Brown and Heron "are consequently led to conclude 
that the diastasic power is a function of the coagulable albu- 
minoids themselves, and is not due, as has been generally sup- 
posed, to the presence of a distinctive transforming agent." 
They further find that filtration through a porcelain diaphragm results in 
the production of a liquid which, on being heated to the boiling point, 
throws down no albuminoids. This filtered malt extract they find to be 
incompetent to produce diastasis, possessing " absolutely no transforming 
power." It is therefore possible to remove the diastasic agent from 
malt extract without the application of heat. 

Barley contains more coagulable albuminoids than does malt, yet fresh 
barley extract exerts but little diastasic action. It is well known that 
malt is prepared by causing barley to germinate, and then kiln-drying the 
grain. This act of germination causes some change in the albuminoids 
by which they are rendered specially active in this respect. It is worthy 
of notice that those parts of the wheat grain of which the soluble albu- 
minoids exert diastasic action (the bran and the germ) are those which 
are more or less directly concerned in the act of germination. 

The comparatively inactive albuminoids of barley, and also wheat, 
may be rendered more efficient as diastasic bodies, after being obtained 
in solution ; and, consequently, independently of germination. If cold 
aqueous infusions of barley and wheaten flours, respectively, have a little 
compressed yeast added to them, and then are allowed to stand for a few 
hours at 30° C, the solution in each case will be found to have consider- 
ably increased in diastasic power. A mixture of yeast and cane sugar, 
under the same conditions, has no action whatever on starch : therefore, 
growing yeast must be considered as capable of producing certain 
changes in the inactive albuminoids of wheat and barley, by means of 
which they are enabled to act on starch. Such action on starch is, 
however, caused by the affected albuminoids, and not by the yeast itself. 
While sttccharomyces act thus on wheat albuminoids, the t>chiz>>uujcete< 
not merely confer no diastasic power, but rapidly destroy that which 
the solutions may have originally possessed. 



94 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



Experimental Work. 

204. Soluble Albuminoids. — Separate a little gluten from flour 
by kneading dough, enclosed in muslin, in water. Dry a little of this, 
and heat strongly in a test-tube ; notice that an odour is evolved similar 
to that of burning hair or feathers. Water also condenses in the cooler 
parts of the tube : test this water with a strip of red litmus paper, and 
notice that it has an alkaline reaction ; this alkalinity is caused by the 
presence of ammonia. Make a precisely similar experiment with some 
white of egg, and observe that the same reactions occur. 

Mix some white of egg with about four times its volume of water. 
Place a portion of this solution in a test-tube, float it in a beaker of 
cold water, and heat gently. Test the temperature at which coagulation 
ensues. To successive portions of the albumin solution, add alcohol, ether, 
mercuric chloride, and picric acid solutions, and dilute nitric acid : notice 
the formation of a precipitate. To the portions precipitated by acid, add 
caustic soda or potash solution : the precipitates are re-dissolved. 

Treat another portion of this solution with acetic acid, and afterward 
with salt, as described in paragraph 189. Also test another portion 
with Fehling's solution : notice that no reaction is produced. 

Weigh out 50 grams of flour, and mix with 250 c.c. of water in a large 
flask, shake up thoroughly several times during half-an-hour, and then 
set aside for a few hours, or even overnight. Filter the supernatant 
liquid through a French filter paper until bright. Heat a portion of 
this solution in a small beaker placed in a water-bath : notice the co- 
agulation of vegetable albumin. Filter this off, and to the filtrate add 
a small quantity of acetic acid : notice that a further precipitate of 
legumin is produced ; remove this also by filtration, and wash it in the 
filter. Heat each of these precipitates in a test-tube ; notice that they 
evolve the same odour as did the white of egg, and that the condensed 
water has also an alkaline reaction due to ammonia. Repeat this ex- 
periment with pea-flour ; notice the relatively large quantity of legumin 
precipitated. 

Test portions of the clear flour infusion with alcohol and the other 
reagents as was done with the white of egg solution ; notice the preci- 
pitation of albumin and its subsequent solution by soda or potash. 

205. Gluten and its Constituents. — The separation of gluten 

will have been illustrated in the preceding experiments. Moisten flour 
with alcohol and fold up in silk ; knead in a small vessel also containing 
alcohol : notice that no gluten is yielded. Make a similar experiment 
with a 15 per cent, salt solution : place a sample of flour for the night 
in the hot water oven, and treat with ordinary water in the morning : 
observe in each case that no gluten is produced. 

Place aside some moist gluten and water in an outhouse ; notice day 
after day the changes which occur in the appearance and physical pro- 
perties of the gluten as putrefaction sets in. 

Effect the separation of gluten into its constituents by Ritthau sen's 
method, and test their properties as described in paragraphs 195-8. The 
extent to which this series of experiments is carried must depend on 
the time and opportunities of the student. 



FERMENTATON. 95 



CHAPTER IX. 

FERMENTATION. 

206. Origin Of Term. — When a little of the substance called 
yeast is added to some wort {i.e., the sweet liquid produced by the in- 
fusion of malt with warm water), at a temperature of about 18° C, it 
induces a most remarkable change. The quiescent liquid, after a time, 
becomes filled with bubbles ; these rise to the surface and form a scum 
there ; as the action proceeds these bubbles are produced with increased 
rapidity. Their continuous ascension gives the liquid a seething or 
boiling appearance, and from this has arisen the application of the term 
"fermentation" to this peculiar phenomenon; that word being derived 
from the Latin "ftrveo," I boil. Fermentation results in a disappear- 
ance of the maltose present in the wort, together with the production 
of alcohol and carbon dioxide gas. The former remains in the liquid ; 
the latter rises to the surface and causes the before mentioned boiling- 
appearance. The carbon dioxide bubbles carry with them to the sur- 
face a peculiar sticky " scum ; " this substance has received the name 
of " Yeast," and on being added to a fresh quantity of wort, is capable 
of setting up fermentation therein. During the fermentation of wort, 
the quantity of this " scum " produced is many times in excess of that 
in the first place added to the wort. 

207. History of the Views held of the Nature of Fer- 
mentation. — The earlier researches and published articles on fermen- 
tation regard that change as one of spontaneous decay. Yeast, with 
which fermentation is associated, was viewed as a peculiar condition 
which nitrogenous matter assumed during one of the phases of its de- 
composition. That in this state it was able to set up fermentation in a 
liquid, which was not at the time fermenting, was noticed as a remark- 
able property of yeast, which nevertheless was still considered as only 
nitrogenous matter in a particular stage of chemical change. One of 
these earlier views ascribed alcoholic fermentation to a vegeto-animal 
substance which resided in grapes as well as in corn. When the grapes 
were crushed, and the flour moistened, this fermentative agent com- 
menced to produce active change. The body thus capable of inducing 
fermentation was termed a " ferment." The next step in investigation 
of this matter was that of Thenard, who observed that the ferment con- 
tained nitrogen, and that in distillation ammonia was yielded ; he there- 
fore ascribed an animal nature to the ferment. (It should be explained 
that the older chemists were in the habit of looking on nitrogenous 
organic matter as animal, and the non-nitrogenous as vegetable ; no 



96 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

reference is intended to the peculiar organic structure of the ferment.) 
Opinion had settled down to the view that yeast was an immediate 
principle of plants, when the microscope, which had become such an 
important factor in scientific research, was brought to bear on the con- 
struction of yeast. The result was a discovery that revolutionised the 
views previously held. It was observed that yeast was a mass of little 
cells, and further, that these were capable of reproduction by a process 
of budding. " Yeast, therefore," said the discoverer, " must be an 
organism which probably, by some effect of its growth, effects the de- 
composition of sugar into alcohol and carbon dioxide." This newly 
discovered form of life was, after some discussion, placed among the 
fungi. The whole problem of fermentation received a most careful and 
exhaustive examination at the hands of Pasteur, who gives as his " most 
decided opinion" that "the chemical action of fermentation is 
essentially a correlative phenomenon of a vital act, beginning 
and ending with it. I think that there is never any alcoholic 
fermentation without there being at the same time organiza- 
tion, development, multiplication of globules, or the continued 
consecutive life of globules already formed." 

This view is in direct antagonism to that of Liebig, who held that the 
cause of fermentation is the internal molecular motion which a body, in 
the course of decomposition, communicates to other matter in which the 
elements are connected by a very feeble affinity. £aid Liebig, " yeast, 
and in general all animal and vegetable matter in a state of putrefaction, 
will communicate to other bodies the condition of decomposition in 
which they are themselves placed ; the motion which is given to their 
own elements by the disturbance of equilibrium is also communicated to 
the elements of the bodies which come in contact with them." Amplify- 
ing this theory, Liebig asserted that the albuminoid bodies decomposed 
spontaneously, and the molecular disturbance resulting from this de- 
composition effected also the decomposition of such bodies as sugar, when 
placed in contact with the decomposing albuminoids. The conclusive 
answer to this position of Liebig's is, that in the absence of minute 
organisms the decomposition of the albuminoids does not occur ; it is 
consequently not spontaneous, and therefore fermentation must be con- 
sidered as a process inseparably associated with the life of certain 
minute organisms. 

208. Definition Of Fermentation. — The particular action pro- 
duced by yeast on wort, and also on the sweet "must," or expressed 
juice of the grape, was found on investigation to be but one of many 
chemical actions which are associated with the life, growth, and 
development of microscopic organisms. Among these may be cited the 
souring of milk, also of wine into vinegar, and likewise the changes 
occurring during putrefaction. Consequently the term fermentation is 
no longer used in its original sense, as signifing a condition resulting in 
a peculiar seething or boiling appearance, but is applied to that group 
of chemical changes which are in Pasteur's words, " correlative 
phenomena of vital acts beginning and ending with them." Used in its 
extended sense, fermentation may be defined as a generic term 
applied to that group of chemical changes which are con- 






FERMENTATION. 97 



sequent on, and inseparable from, the life and development of 
certain minute microscopic organisms. 

In the chapter on the albuminoids, it was stated that putrefaction is 
regarded as a species of fermentation : equally, with the conversion of 
maltose into alcohol by yeast, it is a change inseparable from living 
organisms. Broadly stated, such a change is termed " fermentation " 
when it results in the production of some useful body, and "putrefaction" 
when accompanied by the transformation of a substance into useless 
and offensive products. 

209. Modern Theory of Fermentation. — The following is a 

short statement of this theory. Maltose, albuminoids, and other fer- 
mentable substances do not decompose of themselves, even when sub- 
jected to favourable conditions of moisture, warmth, &c, provided that 
fermenting organisms are rigorously excluded. On the introduction of 
these, they thrive and multiply, taking the nourishment requisite for 
their development from the substance which is fermented. Thus yeast, 
in order to obtain nourishment, attacks maltose (or in strictness the 
glucose produced therefrom), and excretes or voids carbon dioxide gas, 
alcohol, and small quantities of other bodies. The digestive power of 
yeast is limited to converting the sugar into these substances, which 
then become, so fa~ as it is concerned, waste products. Other organisms 
attack the albuminoids and produce butyric acid and other compounds. 
Each particular organism has its special products of fermentation. In 
fermentation, the amount of matter consumed and changed into other 
compounds is excessively great, compared with the size and weight of 
the consuming organisms, consequently a very few yeast globules pro- 
duce a relatively large quantity of alcohol and carbon dioxide. 

210. Experimental Basis of Modern Theory. — It is scarcely 

within the scope of the present work to trace step by step the nature of 
the various researches which have led to the adoption of the theory just 
explained. Briefly stated, the first and most important point is that a 
liquid free from ferment organisms or their germs does not undergo 
fermentation. In proof of this point, liquids were placed in flasks or 
tubes, the necks of which were tightly plugged with cotton wool. The 
liquids were then boiled for some time ; the heat destroyed any organisms 
that might have been present in the liquids or the wool. As the flasks 
cooled, the contained steam condensed ; and air forced its way through 
the cotton wool, which acted as a filter and stopped off any germs that 
might have been floating in the air. Hay and beef infusions, must, 
wort, urine, and other liquids, on being treated in this manner, may be 
kept for any length of time without undergoing fermentation or putre- 
faction. That the resistance to fermentation is due to the absence of 
fermenting organisms, and not to the liquids having been so changed by 
boiling as to be unfit for fermentation to proceed, is proved by adding 
a small quantity of yeast or other ferment to the sterile liquid, when 
fermentation sets in and proceeds vigorously. The chemical changes 
that are produced depend on the nature of the ferment that has been 
added. Yeast effects the decomposition of sugar into alcohol and carbon 
dioxide, other ferments cause putrefaction, and result in the typical 



98 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

bodies characteristic of that change. While these actions are progressing, 
the ferment is found to be developing and multiplying. Further, if the 
ferment used be pure, one species only of organism is found in the liquid. 
Within any possible limits of observation no transformation of one fer- 
ment into another occurs : each belongs to a distinct and separate race 
of organisms. This statement does not deny the possibility of the modi- 
fication of species by means of a natural process of evolution. There is, 
on the contrary, strong evidence in favour of the gradual evolution of 
species in course of time. 

211. Varieties Of Fermentation. — Among the many changes 
included under this term the following are of importance in the con- 
sideration of our present subject : — Alcoholic fermentation, resulting in 
the production of alcohol and carbon dioxide ; lactic fermentation, in 
which sugar is converted into lactic acid ; acetous fermentation, in which 
alcohol is transformed into acetic acid ; viscous or ropy fermentation, 
resulting in the production of mannite and different viscous bodies ; 
and putrefactive fermentation, in which butyric acid and a variety of 
offensive products are formed. 

Alcoholic Fermentation, and Yeast. 

212. The nature of alcoholic fermentation has already been described. 
For the sake of exactness, Pasteur's definition of it is appended. " Al- 
coholic fermentation is that which sugar undergoes under the influence 
of the ferment which bears the name of yeast or barm." When the 
word " fermentation " is employed without any qualifying adjective, 
alcoholic fermentation is always understood. 

213. Substances susceptible of Alcoholic Fermentation. 

— In the strictest sense of the term, the glucoses are, of those bodies 
among the carbohydrates that were described in Chapter VI., the only 
ones capable of alcoholic fermentation. Using the term more widely, 
most of the sugars may be fermented ; in the case of maltose and cane 
sugar, the first step in the change is the conversion by diastasis of these 
bodies into glucose. This change is effected by the soluble albuminous 
matter of yeast, apart from the yeast cell, and therefore is not due to 
fermentation. Pure yeast is incapable of producing fermentation in 
either starch paste or dextrin ; neither can albuminous bodies, whether 
of vegetable or animal origin, be fermented. 

214. Fermentation viewed as a Chemical Change.— The 

conversion of glucose into alcohol and carbon dioxide may be repre- 
sented very simply by the equation — 

C 6 H i2°6 = 2 C 2 H 5 HO + 2C0 2 . 

Glucose. Alcohol. Carbon Dioxide. 

This does not, however, represent the whole of the change, for 100 parts 

of glucose would yield according to this equation — 

Alcohol, ... ... ... 51-11 

Carbon Dioxide, ... ... 48*89 



100-00 



FERMENTATION. 99 



Pasteur carefully collected the whole of the alcohol and carbon 
dioxide produced by fermentation of a definite weight of glucose, and 
found that he only obtained : — 

Alcohol, ... ... 48*51 per cent. 

Carbon Dioxide, ... 46*40 ,, 



100 — 94-91 = 5-09 parts of 
glucose not transformed into alcohol and carbon dioxide. 

The following bodies occur as subsidiary products — glycerin, succinic 
acid ; propyl, butyl and amyl alcohols ; acetic and butyric acids. Of 
these, the amount of glycerin and succinic acid produced have been 
found to be — 

Glycerin, ... ... 3*00 per cent. 

Succinic Acid, ... ... 1*13 ,, 

4-13 
This, therefore, leaves but 0*96 per cent, for the various higher 
alcohols, and the acetic and butyric acids ; and also for that portion of 
the sugar that goes to help to build up fresh yeast cells. 

Monoyer proposes the following equation as showing the production 
of glycerin and succinic acid from glucose — 
4C 6 H 12 6 + 3H 2 = H 2 C 4 H 4 4 + 6C s H 5 (HO) 3 + 2C0 2 + O 

Glucose. Water. Succinic Acid. Glycerin. Carbon Oxygen. 

Dioxide 

No free oxygen is, however, detected in fermentation, any that may 
be produced during the decomposition is probably used up by the yeast 
cells for purposes of respiration. 

Pasteur proves that the glycerin and succinic acid, as well as the 
alcohol and carbon dioxide, are normal products of alcoholic fermenta- 
tion ; and further, that these bodies are produced from the sugar, and 
not from the ferment. He also shows that a portion of the sugar goes 
to help to build up the yeast globules. The quantities of glycerin and 
succinic acid produced are not constant, but vary with the conditions 
under which fermentation proceeds ; when the action is slow the pro- 
portion of glycerin and succinic acid to alcohol is higher than with 
brisk and active fermentation. 

215. Chemical Composition of Yeast.— When yeast has 

been washed carefully so as to free it as far as possible from foreign 
matters, and then dried, it is found to have, according to Schlossberger, 
the following composition — 

Carbon, 

Hydrogen, 

Nitrogen, 

Oxygen, 

Ash (mineral matter), 

100-0 100-0 

In addition to the above a number of other analyses might be quoted, 
.showing that yeast is a body of somewhat variable composition ; mean- 



Surface 


Sedimentary 


Yeast. 


Yeast. 


48-7 


46-4 


6-4 


6-2 


11-8 


9-5 


30-7 


34-5 


2-4 


3-4 



100 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

while attention is directed to the fact that yeast collected from the 
bottom of the fermenting liquid contains less nitrogen and carbon than 
does surface yeast. 

Various attempts have been made to separate yeast into its proximate- 
principles, and estimate these : as a result it may be stated that yeast 
contains one or more bodies of the albuminoid type. There are in addi- 
tion, also present, cellulose and fatty matters. Payen gives the follow- 
ing as the result of an analysis of yeast : — 

Nitrogenous matter, ... ... ... ... 62*73 

Cellulose (envelopes), ... ... ... ... 22-37 

Fatty matters, ... 2*10 

Mineral „ 5"80 

Nsegeli states that the proximate constituents of a sample of yeast 
examined by him were as follows. The yeast was a sedimentary one,, 
containing 8 per cent, of nitrogen : — 
Cellulose, gum, and cell membrane, 
Albuminoids, 
Peptones, ... 

Fat, 

Extractives (leucine, cholestrine, dextrin, 

succinic acid), 
Ash, 

The mineral matter of yeast is of great importance, and has been 
made the subject of careful analysis by Mitscherlich and others. The 
following table gives the composition of the ash of surface and sedi- 
mentary yeasts by Mitscherlich, and of the surface yeast of pale ale by 
Bull— 

Surface Y. Sedimentary Y. 





37 


per 


cent 




45 




5> 




2 




JJ 


... 


5 




JJ 


i, glycerin, 










4 




5) 




7 




5? 





Y 

Mitscherlich. 


Surface Y. of 
Pale Ale. 


Phosphoric acid, P 2 5 , 


53-9 


59-4 


54-7 


Potash, K 2 0, 


39-8 


28-3 


35-2 


Soda, Na 2 0, 


— 


— 


0-5 


Magnesia, MgO, ... 


6-0 


8-1 


4-1 


Lime, CaO, 


1-0 


4-3 


4-5 


Silica, Si0 2 , 


traces 


— 


— 


Iron oxide, Fe 2 3 , ... 


— 


— 


0-6 


Sulphuric acid, S0 3 , 


— 


— 


— 


Hydrochloric acid, HC1, ... 


— 


— 


0-1 



Yeast ash is therefore composed principally of phosphoric acid and 
potash : attention is directed to the similarity in composition between 
the ash of yeast and that of wheat. The above acids and bases probably 
exist in combination as the following salts : — 

Surf. Y. Sed. Y. 

Potassium phosphates, ... ... 81 -6 67*8 

Magnesium phosphate, Mg 3 (P0 4 ) 2 , 16-8 22-6 

Calcium phosphate, Ca 3 (P0 4 ) 2 , ... 2*3 9*7 

The potassium phosphate must be looked on as a mixture of the dihydric 
phosphate, KH 2 P0 4 , and the monohydric phosphate, K 2 HP0 4 . The 
former of these phosphates contains 94, by weight, of K 2 to 142 of 



FERMENTATION. 101 



P 2 5 ; the latter contains 188 of K 2 to 142 of P 2 5 . The weight of 
K 2 in the surface yeast ash is between that required to produce either 
of these two potassium phosphates. The composition of the potassium 
phosphate of the sedimentary yeast ash nearly agrees with the formula, 
KH,P0 4 . 

216. Yeast as an Organism. — Viewed as an organism, yeast 
may be said to be a plant of an exceedingly elementary structure ; it is 
in fact one of the simplest plants known. In very minute forms of 
life it is difficult to distinguish animals and vegetables from each other, 
for with almost any definition that may be selected, one or two species 
wander over the border line. One of the most marked differences 
between plants and animals is, that the former are able to derive their 
sustenance from inorganic compounds, their carbon from carbon dioxide, 
and their nitrogen from ammonia. Animals, on the contrary, can make 
no use of carbon or nitrogen for the purpose of building up their tissues, 
unless these bodies are presented to them in the form of organic com- 
pounds. Hence, in the economy of nature, it will be found that while 
plants live and develop, as before stated, by the assimilation of the 
elements of carbon dioxide and ammonia, animals subsist either on 
vegetable substances, cr on the bodies of other animals. Yeast being 
able to derive its nutriment from inorganic bodies, is placed in the 
vegetable kingdom. The chemical changes produced during the growth 
of plants result in the building up of complex compounds from very 
simple ones : in the animal, complex bodies are required as nourishment, 
and are broken down into simpler bodies. The complexity here referred 
to, is that which may be measured by the number of atoms in the molecule 
of the body ; thus water is a very simple compound, while starch has a most 
complex molecular structure. The chemical operations of plant-life may 
be summed up as consisting of synthesis ; those of animal existence as 
analysis. In order to effect the synthesis of plant compounds from the 
substances at the disposal of vegetables, force is required ; this they 
usually obtain in the form of heat from the sun. The act of growth of 
a plant means, therefore, a continual absorption of heat. On the other 
hand, animals, in taking complex bodies and breaking them down into 
simpler ones, liberate heat ; consequently, one result of animal life is 
that heat is continuously being evolved. Yeast, in this particular, 
behaves more like an animal than a plant, for during fermentation the 
temperature of the liquid rises considerably. Although yeast as a plant 
possesses and exercises the power of building up higher compounds from 
the simpler ones, yet it at the same time breaks down some of the 
compounds, with which it is in contact, into simpler bodies ; and so, by 
the liberation of heat, raises the temperature of the containing liquid. 
From a chemical standpoint, yeast combines in itself the vegetable func- 
tions of synthesis, with the animal functions of analysis. 

217. Botanic Position of Yeast. — This organism belongs to 

the family of Fungi. 

Fungi. — The fungi are those plants which are destitute of chlorophyll 
(the ordinary green colouring matter of grass, &c.) They reproduce by 
buds and spores. 



102 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Spores. — Spores are a variety of cell, and in all fungi the spores are 
similar in essential points to the yeast cell ; notwithstanding that they 
may vary considerably in appearance and details of structure. 

Hyphce. — The spore, on being sown in a suitable medium for its 
growth, throws out a long delicate stem of tubular structure, termed 
a " hypha." A group of these hyphse constitute the fungus. 

Mycelium. — One of the best typical examples of a fungus is the 
common green mould found on old boots, bread, jam, &c. This has 
received the name Penicillium glaucum. On examining a specimen of 
such mould from the top of a pot of jam for instance, its base is found 
to consist of an interlaced growth of hypha?, forming a more or less com- 
pact web or skin on the jam, This layer of intermingled hyphse is 
termed the " mycelium." From its upper surface a number of hypha? 
project into the air, each bearing a quantity of very fine green powder, 
these are termed " aerial hypha?." On the lower surface again, other 
hyphse grow down root-like into the liquid, which supports the mould , 
these are the " submerged hyphse." 

Conidia. — Some of the serial hyphse terminate in short branches, each 
of which is divided into a series of rounded spores which are only loosely 
attached to the hyphse, and so may easily be shaken off, these spores 
are termed " conidia." Each separate conidium, if sown in a suitable 
liquid, develops a young fungus, which in its turn rapidly multiplies. 

Sporangia. — Some of the fungi, as for instance that known as Mucor 
mucedo, have their hyphse terminated in rounded heads ; each of these is 
called a " sporangium." 

218. Varieties of Yeast. — The yeast fungi constitute the genus 
Saccharomyces, they are so named because they mostly live in saccharine 
solutions, converting the sugar present into alcohol. The saccharomyces 
have no mycelium, and in common with the other fungi reproduce by 
buds and spores. The genus saccharomyces comprises several species, of 
which the following are the most important : — 

Saccharomyces Cerevisia?, ... J & 

,, Minor, ... Ferment of Leaven. 

,, Ellipsoideus, Ferment of Wine. 

„ Pastorianus. 

219. Saccharomyces Cerevisiae, or ordinary Yeast — At 

least two distinct varieties of ordinary yeast are known, to which the 
names of " High " and " Low " yeast have been given. Pasteur con- 
siders these two to be distinct species ; this view by later authorities 
is deemed untenable. The former of these is the common yeast of 
English ale fermentation; the other, that of the well-known "lager" 
beer of continental production. Saccharomyces minor, a species of yeast 
found in leaven, is also in all probability a sub-variety of S. cerevisice, 
so,, too, is the kind of yeast imported so largely in this country from 
France and Germany, and sold as compressed yeast. 

220. High Yeast. — This organism consists of cells, mostly round, 
or slightly oval, from 8 to 9 mkms. in diameter ; the cells may occur 
either singly or grouped together in colonies. These cells have a dis- 



FERMENTATION. 103 



tinct wall or envelope of cellulose, and contain within their interior a 
more or less gelatinous mass of matter devoid of organic structure. The 
interior substance is named " protoplasm ) " this term being applied to 
that ultimate form of organic matter of which the cells of animals and 
plants are composed. The protoplasm of the yeast cell is not homo- 
geneous, but is always more or less distinctly granular. One or more 
circular spots can usually be seen in yeast cells as obtained from a 
brewery ; these are paused by the gelatinous matter moving toward the 
sides of the cell, and leaving a comparatively empty space ; hence these 
spots are termed vacuoles. A specimen of yeast is figured below : — 




figure 7. — Saccharomyces Cerevisice. 
a, a bud-colony ; b, two spore-forming cells (after Lurssen). 

221, Life History. — On examining under a microscope a sample 
of skimmed yeast, as obtained from the brewer, it is found to consist 
either of single cells or cells joined together in pairs. Such yeast 
having usually remained quiescent for some time, the cells rarely occur 
in large groups, because, with standing, they tend to separate from 
each other. The granulations in the protoplasm, and also the vacuoles, 
should be visible. On placing a very small quantity of this yeast in a 
suitable liquid for its growth, as malt wort, at a temperature of about 
30° C. (86° F.), the cells, which at first were somewhat shrunken and 
filled throughout with granular matter, increase in size from absorption of 
the liquid in which they are placed. At the same time the granulations 
become less distinct, and the whole cell assumes a more transparent and 
distended appearance. This effect may be easily watched by first exa- 
mining a few cells in water under the microscope, and then mounting 
a few more on a fresh slide with warm malt wort ; the changes de- 
scribed may then be followed on the stage of the microscope. After a 
time the round yeast cells become slightly elongated through the 
formation of a small protuberance at one end ; this grows more marked, 
until shortly a neck is formed by a contraction of the cell wall. But 
still, careful examination shows that there is a distinct opening through 
this neck, the contents of the smaller portion being continuous with 
those of the cell. As the growth continues, the strangulation at the 
neck proceeds until the cell wall completely shuts off the protuberance, 
which then constitutes a new or daughter cell, attached to the parent. 
This operation is known as " budding." The one parent cell is capable 
of giving off several buds in succession ; but after a time its reproductive 
energy is exhausted, and the cell breaks up. These daughter cells in 



104 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



their turn give rise to other cells, and so the multiplication of yeast 
globules proceeds with remarkable rapidity. 

Pasteur states that on one occasion he watched two cells for two 
hours, during that time they had multiplied by budding into eight, in- 
cluding the original pair of cells. At this stage, buds of every size may 
be seen attached to the parent cells ; some are so small as to be scarcely 
visible, while others are nearly as large as the parents. 




High Yeast, at res>t ; b, 



FIGURE 8. — Saccharomyces Cerevisicz. 

Low Yeast, at rest 



High Yeast, actively budding 
Low Yeast, actively budding. 



With the progress of this growth and development, sugar is being 
decomposed, the liquid becomes alcoholic, and its specific gravity 
diminishes. The brewer terms this change " attenuation," or a becom- 
ing thinner. Another reason for the use of this name is that the liquid 
becomes less viscous, from the conversion of the syrupy solution of mal- 
tose into the highly mobile liquid, alcohol. Simultaneously with the 
production of alcohol, carbon dioxide gas is evolved ; this rapidly rises to 
the surface, and carries up with it the yeast cells, which float on the top 
of the fermenting wort. Yeast now skimmed off is found to consist of 
colonies of some scores of cells linked together ; the majority of these are 
clear and almost transparent. Usually, in the middle of each such 
group, the old or parent cell can be recognised by its darker contour 
and comparatively exhausted appearance. As the quantity of sugar in 
the liquid becomes less, the fermentation slackens and finally ceases. 
If the cells then be again examined under the microscope, they will 
be found to have a firmer outline, and their contents will be more 
granular. In what may be termed old age of the yeast cell, the walls 



FERMENTATION. 105 



become abnormally thick, and the granulations very dense. The yeast, 
on being removed from the fermenting tun, is usually set aside in store 
vats ; on standing, it gradually assumes the appearance described on that 
of the yeast used for " pitching " or starting the fermentation. The 
quantity of yeast thus obtained is considerably in excess of that first 
-added to the malt wort. 

In the moist state, yeast decomposes quickly ; hence if the store be 
kept for any length of time, the cells rapidly alter in character. The 
walls become soft, thin, and weak, and the interior protoplasm changes 
irom its normal granular gelatinous condition to a watery consistency. 
Thorns states that after a time, if viewed with a high power (^V-inch 
objective), the contents of the cell are seen to be in rapid motion. The 
motion of liquids per se not being observable, this effect must be due to 
the suspended debris of the cell, consisting probably of minute fragments 
-of cellulose from the envelopes. After a time the walls also break down 
and all traces of the yeast organism disappear. The normal bodies 
produced by the decomposition of nitrogenous and albuminous bodies 
may now be detected in the liquid : putrefaction rapidly follows, with the 
production of a most offensive odour. Such is in broad outlines the life 
history of a yeast cell, when sown under normal conditions in malt wort. 

High yeast produces a beer having a special and characteristic 
flavour, which distinguishes it at once from beer brewed with low yeast. 

222. Influence of Temperature on Yeast Growth. — The 

temperature most favourable to the growth of yeast is from 25° C. to 
35° C. (77° and 95° F.) Between these points yeast flourishes and grows 
well ; at temperatures lower than 25° growth proceeds, but not so 
rapidly. At a temperature of about 9° C. (49 -6° F.), the action of yeast 
is arrested ; the vitality, however, of the cell is only suspended, not 
destroyed, for with a higher temperature it again acquires the power of 
inducing fermentation. Actual freezing does not destroy yeast, pro- 
vided the cells do not get mechanically ruptured or injured. Above 
35° C, the effect of heat is to weaken the action of yeast, until at a 
temperature of about 60° C. (140° F.), being that at which albumi- 
noid principles begin to coagulate, the yeast is destroyed. This applies 
to moist yeast. When dry, the cells are able to stand higher tempera- 
tures than when suffused with water ; thus dried yeast has been heated 
to 100° C. without destroying its vitality. 

Although a temperature of from 25° to 35° C. conduces to the rapid 
growth of yeast, yet there are other circumstances which render it ad- 
visable to conduct actual brewing operations at a much lower tempera- 
ture. In English breweries, a pitching temperature of about from 
18° to 19° C. (65° F.) is commonly employed : during th3 fermentation 
the heat rises to from 21° to 22° C. (72° F.) 

Faulkner states that a tun of pale ale, containing 200 barrels of 36 
gallons, on being pitched with 600 lbs. of yeast at 14-5° C. (58'1° F.) had 
sufficiently attenuated in 46 hours, during which time the temperature 
had risen to 22-2° C. (72° F.) 

223. Substances Requisite for the Nutriment of Yeast — 

It has several times been stated that sugar is required by yeast during 



106 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

its growth ; as yeast cells likewise contain nitrogenous matter, and 
also certain inorganic constituents, it is evident that nitrogen in 
some form, and also the requisite mineral salts, must be supplied to the 
growing yeast. Summing these up, yeast requires for its growth, sugar, 
nitrogenous compounds, and appropriate inorganic matter. 

224. Saccharine Matters. — These occupy the first and paramount 
position, as being absolutely necessary for the production of alcoholic 
fermentation. Pure yeast sown in a pure sugar solution causes it to 
ferment ; but without the sugar neither alcohol is produced nor carbon 
dioxide evolved. Malt wort, grape juice or " must," and dough all fer- 
ment on the addition of yeast, because they all contain sugar. "It is 
necessary indeed that sugar be present ; for if we abstracted 
by some means or other from the must or dough all the sugar 
contained in it *[and also all substances capable, by the 
addition of yeast to flour, of being converted into sugar], 
without touching the other constituents the addition of yeast 
would produce no gas. Everything would remain quiet until 
the moment when signs of a more or less advanced putrefac- 
tion showed themselves." (Pasteur). It should be mentioned 
that yeast is also capable of inducing definite chemical changes in a few 
other bodies, among these is malic acid, which is broken up into 
succinic and acetic acids, carbon dioxide, and water. It is also stated 
that yeast decomposes glycerin into propionic and acetic acids ; this 
change has been denied by Roos and Brown. As neither malic acid 
nor glycerin (in the free state) occur as constituents of flour, their 
fermentation lies altogether outside the scope of the present work. 

The glucoses, or sugars of the C 6 H 12 6 group, are the only sugars 
capable of direct fermentation, of these dextrose is more readily decom- 
posed by yeast than is laevulose. The two being together in the same 
solution, it is stated that the hevulose remains unacted on until the 
disappearance of the whole of the dextrose. Certain other sugars are^ 
capable of indirect fermentation by yeast ; among these are cane sugar 
and maltose, they are first, however, hydrolised to glucose by the action 
of the zymase or soluble diastasic body secreted by the yeast cell. This 
preliminary diastasis can be effected by yeast water, that is, water with 
which yeast has been shaken up, and then filtered in order to remove 
the whole of the yeast cells ; such yeast water is of course totally in- 
capable of setting up alcoholic fermentation. 

Yeast causes certain effects, of which it is difficult to say whether they 
are absolutely correlatives of vital acts as on organism, or merely results 
of diastasis. For practical purposes it matters little to which of these 
two classes of chemical action any specific change produced by yeast 
belongs ; in such cases it is the action of yeast as a whole that is of im- 
portance. 

Sugar of milk is incapable of fermentation by yeast. Yeast alone is- 
also unable to ferment either starch paste or dextrin, these bodies 
require some more powerful agent for their diastasis, such as malt 
extract. As mentioned in chapter VIII. , yeast, indirectly through its. 

* The clause in brackets, [ 1 , is inserted by the author. 



FERMENTATION. 107 



action on the albuminoids of barley or wheaten flour, transforms starch 
paste into dextrin and maltose, after which the yeast induces fermenta- 
tion. Consequently, the two, yeast and albuminoids, in conjunction, 
are capable of effecting changes which neither can separately produce. 

It almost goes without saying that water is necessary for the develop- 
ment of yeast, so requisite is it that saccharine solutions containing over 
35 per cent, of sugar are incapable of fermentation. Such a solution, 
by osmose through the cell wall, deprives the yeast of its normal pro- 
portion of water as a constituent. 

225. Nitrogenous Nutriment. — Yeast is capable of utilising, 
during its growth, the nitrogen of ammoniacal salts ; thus a solution of 
pure sugar, mixed with either ammonium tartrate or nitrate, and cer- 
tain non-nitrogenous inorganic salts, permits a healthy development of 
yeast. With the multiplication of the yeast cells, the amount of albu- 
minous matters present increases ; therefore, by the action of yeast, the 
ammonium compounds are transformed into albuminous bodies. Al- 
though yeast thus acts on ammonium salts, organic nitrogenous com- 
pounds form a more suitable nutriment ; among such substances, the 
soluble albuminoids of yeast itself are especially seized on by yeast. 
Consequently, always supposing the presence of the inorganic salts re- 
quired by yeast, yeast water and sugar form an admirable medium for 
its growth and development ; so too, do natural saccharine juices, as 
must, the juice of apples, pears, &c. In addition to these, malt infusion 
must be mentioned. 

Albumin, whether from the white of egg or vegetable albumin, is 
entirely unfit for the nourishment of yeast. This fact is stated with 
force by Pasteur, whose opinion is confirmed by that of Mayer, who 
ascribes the inactivity of albumin, casern, and other similar bodies, to their 
highly colloid nature. The solution molecules of soluble albuminoids of 
malt have such an appreciable volume that filtration of the solution 
through a thin porous earthenware diaphragm under slight pressure is 
sufficient to prevent these bodies from passing through into the filtrate 
(Brown and Heron). It may then be readily understood that yeast 
cell walls are impermeable to albuminoid bodies. The compounds pro- 
duced by digestion of albumin and its congeners — the peptones, are 
much more diffusible, and are eminently suited for affording the requisite 
nitrogenous nutriment to yeast. Pepsin itself forms an admirable 
yeast food. Schutzenberger considers it probable that must, malt wort, 
and yeast water owe their power of nourishing the cells of yeast, not to 
the albuminoid bodies, but to certain of their constituents that are 
analogous to the peptones, and which have the property by osmose of 
passing through the cell walls. 

226. Mineral Matters necessary for the Growth of 

Yeast. — For his experiments on yeast, Pasteur used yeast ash as the 
source of his mineral matter. It is obvious that this substance may be 
replaced by an artificial mixture of the salts contained therein. A 
reference to Mitscherlich's analyses of yeast ash shows that the prin- 
cipal ingredient is potassium phosphate ; together with this there is 
magnesium phosphate and small quantities of phosphate of calcium. 



108 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Pasteur finds, when an unweighable quantity of yeast is sown in a solu- 
tion of pure sugar and ammonium tartrate, that development of cells 
^ind fermentation do not take place ; the addition of yeast ash enables 
both to occur. Mayer endeavoured further to ascertain what salts are, 
in particular, necessary among those present in the ash. Potassium 
phosphate is absolutely indispensable ; neither sodium nor calcium phos- 
phates are competent to replace it. Magnesia is also of great value, if 
not indispensable, to the development of yeast ; this base may be sup- 
plied either as sulphate or phosphate. Lime seems not to be absolutely 
necessary to yeast growth. 

227. Insufficiency of either Sugar or Nitrogenous Matter 

Only for the nutriment Of Yeast. — Yeast is incapable of healthy 
•development in solutions of sugar alone. A limited growth occurs 
when the quantity of yeast added is considerable, because, by a species 
of cannibalism, the healthier and stronger cells survive and develop to 
some extent by feeding on the nitrogenous and mineral matters obtained 
from the others. Necessarily, such growth must soon stop. Yeast was 
found by Pasteur to multiply in a nitrogenous liquid, such as yeast 
water, " even when there was not a trace of sugar present, provided 
always that atmospheric oxygen is present in large quantities." Yeast 
finds air to be under these conditions an absolute necessity. Without 
it no development proceeds, nor is there any but the slightest trace of 
alcohol found ; carbon dioxide gas is evolved, being formed by direct 
carbonisation of oxygen derived from the air. But, for this change, it 
must be remembered that air is a necessity. Further, the conversion of 
oxygen into carbon dioxide gas results in no change of volume ; this is 
clearly seen by reference to the molecular equation — 
C + 2 = CO ? . 

Carbon. Oxygen. Carbon Dioxide. 

Under ordinary conditions of fermentation, albumin does not evolve 
alcohol or carbon dioxide gas. Neither does pepsin when similar ty treated, 
although this body is well adapted as a nitrogenous food for yeast. 
Albumin is also unacted on when its solution is first of all mixed with 
a 2 J per cent, solution of sodium chloride. 

228. Behaviour of Free Oxygen on Yeast.— Again quoting 

Pasteur as an authority, he states as a result of experiment that yeast 
grows better in shallow than in deep vessels. As a result of some deter- 
minations made, in which one sample of yeast and a saccharine solution 
were kept in an air-free flask, and another in a shallow vessel, by which 
it was freely exposed to the atmosphere, he finds that the proportion of 
yeast produced to the sugar consumed was much greater in the latter 
than in the former instance. By dint of most careful experiment he 
further finds, while a fermentable liquid may be made to ferment out of 
contact with air, yet in order that it shall do so it is essential that 
young and vigorous yeast cells shall be employed. With older yeast the 
fermentation proceeds more slowly, and with the production of mal- 
shaped cells, while a yeast still older is absolutely incapable of repro- 
duction in a liquid containing no free oxygen. This is not due to the 
yeast being dead, for on aerating the liquid, either with atmospheric air 



FERMENTATION. 109' 



or oxygen, fermentation proceeds apace. Pasteur conclusively proved 
that under favourable circumstances yeast functions as a fungus ; that 
is, it lives by direct absorption of oxygen from the air, and the return 
of carbon dioxide gas. The relation between its life in free oxygen and 
its life when submerged in a sugar solution is extremely interesting. 
Let some yeast be sown in a sample of malt wort, containing as much 
oxygen as it can possibly dissolve ; the yeast starts active growth, and 
rapidly removes all the free oxygen from the liquid, after which it com- 
mences to attack the sugar. During this time, yeast will be living not 
as a ferment but as a fungus, namely, by direct absorption of oxygen. 
Could each yeast cell be supplied with all the oxygen it requires in the 
free form, it is probable that it would not exert the slightest fermenta- 
tive action ; it would, at the same time, grow and reproduce active- 
healthy cells with great rapidity. As soon as the whole of the air is. 
exhausted, the yeast attacks the sugar, and obtains its oxygen by the 
decomposition of that compound, and ordinary fermentation proceeds. 
Consequently, yeast must be viewed as being capable of two distinct 
modes of existence, in free oxygen as a fungus; when submerged in a 
saccharine solution, as a ferment. Of the two the fungus life is the 
easiest ; that is, yeast can perform its vital functions more readily 
when it obtains its oxygen in the free state than when it has for that 
purpose to effect the decomposition of large quantities of sugar. If 
yeast be grown continuously in saccharine solutions, under conditions 
which result in the rigid exclusion of air, fermentation becomes more 
and more sluggish : the conditions of life are in fact more severe than 
the yeast can stand, the struggle for existence is too acute, and its 
vitality succumbs. But if a sample of fermenting wort be taken at a 
time when, although the sugar is far from exhausted, the fermentation 
has become sluggish, and then thoroughly serated by some means 
which shall bring it into full contact with air, a remarkable change 
ensues. At first the fermentation slackens, but the rate of growth of 
yeast increases ; this is due to its living as a fungus on the dissolved 
free oxygen. During this time it exerts little action as a ferment, but 
grows and accumulates vital energy. After a while, the fermentation 
proceeds much more vigorously than before the oration ■ this is a neces- 
sary result of the renewed energy and vitality of the yeast cells. To 
borrow an illustration, a working diver, enclosed in a water-tight helmet 
and dress, when performing his duties at the bottom of the sea, lives 
under difficulties. His submerged state renders breathing difficult, and 
any work on which he may he engaged, exhausting : after a limited 
time it is absolutely necessary for him to return to the fresh air. ISTow, 
during the time he is thus at rest, functioning as a fungus (if the com- 
parison may be permitted without disrespect to those engaged in a most 
responsible and hazardous business), his work at the bottom is station- 
ary ; yet it on the whole profits by his rest, for shortly, with increased 
vigour, he is again able to resume work, and that with activity and 
increased effect. The comparison is obvious, and may assist to a more 
thorough grasping of this relation of free oxygen to fermentation. 

Long before Pasteur had demonstrated the effect of oxygen in this 
way as a stimulant to fermentation, brewers had found that by " rousing "' 



110 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

(stirring) tuns of wort that were fermenting sluggishly, the fermenta- 
tion was invigorated. The agitation following from this rousing aerated 
the wort. 

When the object of fermentation is to produce yeast, rather than 
alcohol, aeration of the worts should be encouraged to the fullest extent ; 
in yeast factories, where this is one of the principal objects, fermentation 
is conducted in large shallow vats, whereby the surface exposed to the 
air is much increased. 

This growth of yeast as a fungus, so clearly established as a fact by 
Pasteur, is of great interest as showing the close relation this organism 
bears to the great fungus family, not only in form, mode of growth, &c, 
but also in its physiological functions. To borrow his own words, 
" fermentation by yeast is the direct consequence of the processes of 
nutrition, assimilation, and life, when these are carried on without the 
agency of free oxygen. . . . Fermentation by means of yeast appears, 
therefore, to be essentially connected with the property possessed by 
this minute cellular plant of performing its respiratory functions, some- 
how or other, with oxygen existing combined in sugar. Its fermentative 
power varies considerably between two limits, fixed by the greatest and 
least possible access to free oxygen which the plant has in the process of 
nutrition. If we supply it with a sufficient quantity of free oxygen for 
the necessities of life, nutrition, and respiratory combustions, in other 
words, if we cause it to live after the manner of a mould, properly so 
called, it ceases to be a ferment ; that is the ratio between the weight of 
the plant developed and that of the sugar decomposed, which forms its 
principal food, is similar in amount to that in the case of fungi. On 
the other hand, if we deprive the yeast of air entirely, or cause it to 
develop in a saccharine medium deprived of free oxygen, it will multiply 
just as if air were present, although with less activity, and under these 
circumstances its fermentative character will be most marked ; under 
these circumstances, moreover, we shall find the greatest disproportion 
all other conditions being the same, between the weight of yeast formed 
and the weight of sugar decomposed. Lastly, if free oxygen occur in 
varying quantities, the ferment power of the yeast may pass through all 
the degrees comprehended between the two extreme limits of which we 
have spoken." Such is Pasteur's admirable resume of the phenomenon 
of fermentation as one phase of the act of vitality. 

Pasteur suggests fungi, as plants living with access to air, should be 
called "aerobian" plants, and that the term "anaerobian" should be 
applied to those organisms which function in the absence of air. 
Yeast, accordingly, is spoken of as being capable of both an aerobian 
(fungus-like), and an anaerobian (ferment-like) existence. 

229. Mai-Nutrition Of Yeast. — When yeast is deprived of a 
normal proportion of each of the necessary constituents for its healthy 
life, the vitality of the cells is thereby lessened. One result of this is 
that the cells tend to assume abnormal forms. Thus, when grown 
without access of free oxygen, yeast cells elongate, and at times are 
observed to be several times as long as broad (sausage-shaped). The 
same peculiarity of outline may be noticed in yeast that has been grown 
in sweetened water. The reason may be that, with a deficient supply of 



FERMENTATION. Ill 



nutriment, each cell stretches itself out, as it were, in order to expose 
as great a surface as possible to the medium. It is well known that the 
area of surface of a sphere is less in proportion to its cubical contents 
than is that of a cylinder or of any other solid body. By offering a 
greater surface to the liquid in which it is growing, the yeast cell pre- 
sumably is enabled to absorb a greater amount of nutriment. In 
breweries where sugar is largely used as a substitute for malt, the yeast 
suffers from the low percentage of nitrogenous matters contained in the 
wort : the result is that such yeast has little vitality and is soon ex- 
hausted. 

Large quantities of mineral salts also affect the shape of the yeast 
cell ; thus, the yeast of Burton ale is oval (egg-shaped) in outline : the 
Burton water is extremely hard, containing calcium sulphate in large 
quantities. 

Badly nourished yeast, on examination, is usually found to have 
abnormally thin and fragile cell walls, these being broken by the 
slighest pressure ; the contents of the cells are also thin and watery, 
instead of full of healthy granulations of gelatinous protoplasm. 

230. Reproduction of Yeast, other than by Budding.— 

Some of the earlier writers on yeast maintained that the phenomena of 
budding seen during the growth of yeast is merely an optical illusion, 
and that what actually occurs is that the parent yeast cell breaks up, 
and that the granular contents attach themselves to the sides of other 
cells and then develop into full-sized cells. That this view is incorrect 
is proved by its being possible when yeast is budding to observe that 
the interior of the parent-cell and the bud is continuous, their being, at 
first, a direct opening from one into the other. Further, in the midst 
of a colony of young cells, the old or parent-cell is still seen intact. 
Pasteur combats the theory of the breaking up of the parent-cells most 
vigorously, and asserts that " this breaking is really of the most rare 
occurrence, and may always be explained by some abnormal circum- 
stance affecting the yeast ; being, indeed, a mechanical accident, not a 
physiological fact." This much may be granted to Pasteur, that the 
normal growth of yeast, when sown in a saccharine fluid, such as wort, 
or must, is by budding ; and that disruption of the cells occurs most 
rarely. But the growth of yeast is not, either in the laboratory, or in 
technical operations, confined to the fermenting of fluids such as wort 
or must. Pasteur seems to have altogether ignored other environments 
in which yeast behaves far differently. Schiitzenberger quotes, and 
without contradiction, de Vaureal's opinion that the supposed budding 
is only an optical delusion, and that the granulations are spermatia 
(spores), which, when set free by the rupture of the envelope, produce 
new yeast cells. Schiitzenberger goes on to view this mode of multipli- 
cation as explaining " the facility with which the reproductive elements 
of yeast can be carried by the air, when we cannot distinguish in air-dust 
any characteristic globules of yeast." The assertion of de Yaureal's 
that the budding is an optical delusion cannot be maintained ; but there 
is very strong evidence that reproduction can also take place in the 
manner he describes. When ale, such as Bass's, is bottled, there is always 
a small quantity of yeast still present ; hence, if a trace of the sediment 



112 CHEMISTEY OF WHEAT, FLOUR, AND BEEAD. 

from a newly bottled sample is examined under the microscope, yeast 
cells can be distinguished. But if the bottle is an old one, the most 
careful examination only reveals the presence of isolated cells, or none 
at all. Instead, there are found a number of minute granules that 
could not be recognised as saccharomyees ; these consist of the granular 
contents of the cells. 

Thorns has probably devoted more time than any other living observer 
to the microscopic study of the functioning of yeast in dough and bakers' 
barms. In a review of his on Chicandard's Theory of Panary Fermenta- 
tion, he makes some interesting statements which have an immediate 
bearing on the present topic. This theory, and Thorn's reply to the 
same, will be dealt with fully later on ; meantime there follow certain 
extracts from Thorn's article. 

" All our bread is fermented with flour barm, which is simply a modi- 
fication of leaven, and I have never found Saccharomyees absent in such 
dough. But there is this difference between the barm-leaven of Scot- 
land and the leaven of France : — The barm-leaven may be called a semi- 
fluid, in which, during the active stage of barm fermentation, the 
saccharomyees or yeast cells, reproduce by buds, followed slowly, during 
the resting or inactive stage, by a resolution of the protoplasm of the 
cells into spores ; the French leaven, on the other hand, may be called 
a semi-solid, in reality a bit of old dough, in which it will be found that 
reproduction by budding is the exception, and reproduction by spores 
the rule. Now, when spore-bearing cells are, as in France, introduced 
direct without ferment — I refer to a potato, or a flour " ferment " — into 
semi-solid dough, the old cells are broken up, within one to three hours, 
in giving birth to the spores, and the search then, and for hours after, 
for cells having the physical features of S. minor or S. cerevisice may be 
taken as hopeless. This sporular reproduction is not confined to varie- 
ties of leaven. All the numerous varieties of yeast examined by this- 
writer (Thorns) are subject to it, hence we see the reason for the apparent 
" gradual diminution " of the cells in yeast dough, referred to by M.. 
Chicandard, when the examination takes place before the young spores 
have had time to acquire the physical features and size of the parent 
cells. This phase of the subject M. Chicandard has either not known 
or overlooked. 

" Proof of my statements may be obtained by placing a trace of, say 
Paris-pressed yeast, 24 to 36 hours old, or after packing by the manu- 
facturer, on a glass slide, diluting it with water and keeping at a 
temperature 70° to 76° F. under continuous microscopic observation 
for from one to three hours with eye-piece and objective — immersion, 
used without cover-glass — amplifying from 1000 to 2000 diameters. At 
first nothing but the yeast cells (and too often starch granules in excess) 
in the water can be seen. The cells are motionless, containing sporules 
of various sizes and in varying numbers in each cell, and if healthy, 
with only traces of undifferentiated protoplasm in some of the cells. As 
the observation is continued, the cells are seen to increase in size by the 
absorption of water, the sporules to begin a more or less active move- 
ment within the cells, which continues and may become more active, 
the cell walls grow thinner, till, within one to three hours, they are; 



FERMENTATON. 113 



dissolved or disappear, and the active sporules are free. These are then 
seen to be mostly single \ but some few in pairs, rolling about with an 
active Brownian movement — little more than rolling from side to side, 
very slightly translative — and when freed from unhealthy cells {i.e. cells 
with none, or one or two small sporules and the rest of the protoplasm 
in seething, boiling motion), they are seen accompanied by numerous 
small organisms, motile, of variable length, some single, some in pairs; in 
other words, the organisms seen by M. Chicandard in leaven and yeast 
doughs, and which he considers like bacteria, and in this I agree with 
him. The released sporules from healthy cells are so small, and with 
protoplasm so transparent and non-granular that, seen in diluted or 
filtered yeast or leaven doughs, they would not be recognised as Saccharo- 
mycvs. But we see, nevertheless, that they are the endogenous off- 
spring or spores of yeast. I reaffirm spores of yeast, because, continu- 
ing the observation, we find within the second and third hour the whole 
microscopic field of view covered with these minute active cells ; the 
difficulty then is to find a large old cell, the earlier released spores have 
become larger, slightly oval, with minute buds in process of formation. 
They are budding saccharomyces, requiring only time and a medium, 
such as sterilised malt wort, to acquire the functions, size, and appear- 
ance of their parents. The old cells die in giving birth to a progeny six 
to eight times their number, but the young do not die in the dough if 
properly treated ; on the contrary, they, in due course, live their short 
lives, assimilating, excreting, respiring, growing big, then resting a little, 
and finally resolving their protoplasm into spores." (Thorns, British and 
Foreign Confectioner, March, 1885.) 

This observation of Thorns', be it noted, is in substantial agreement 
with those of de Vaureal and Schutzenberger, so far as the possibility 
of the reproduction of yeast in the absence of normal yeast cells is 
concerned. 

Huxley fully recognises that yeast reproduces by spores — " No Torula 
(yeast cell) arises except as the progeny of another ; but, under certain 
circumstances, multiplication may take place in another way. The 
Torula does not throw out a bud, but its protoplasm divides into (usually) 
four masses, termed ascospores, each of which surrounds itself with a 
cell-wall, and the whole are set free by the dissolution of the cell- 
wall of the parent. This is multiplication by endogenous division." 
(Practical Biology, Huxley and Martin, p. 4.) In the same work are 
given directions for the study of endogenous division. Some dried yeast 
is to be first washed, then allowed to subside : the supernatant liquid is 
poured off, and the creamy deposit, spread with a camel's hair brush in 
a thin layer on either freshly cut potato slices or on a plate of plaster 
of Paris. It is then placed under a bell jar, together Avith wet blotting 
paper. Usually, on about the eighth or ninth day, ascospores make 
their appearance, and may be detected by examination with a power 
of about 800 diameters. Cells containing ascospores are shown in 
Figure 7. 

With sound yeast to start with, Thorns' estimate of the time before 
sporulation occurs is extremely short : the author finds that cells of 
yeast sown in either water or an unfermentable medium, and maintained 



114 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

for some three or four days at a temperature of 25° C, stili maintain 
their cell walls intact. 

In Huxley's experiment, the wet blotting paper is used in order to 
keep the atmosphere of the bell jar saturated with moisture, and so pre- 
vent the yeast drying up. 

The breaking up of yeast with the liberation of granules occurs when 
the cells are in an exhausted medium, as finished beer ; or one in which 
there is little yeast nutriment, as in dough. In dough, too, the difficulty 
of growth is increased by its semi-solid condition. These granules, if 
sufficiently developed, before the breaking of the parent cell, to maintain 
an independent existence, grow and bud as ordinary yeast in a suitable 
medium. Endogenous division also ensues when the yeast is exposed to 
air, or moist surfaces, whether of potato or plaster of Paris. Further, 
when yeast is allowed to dry the cell envelopes also disappear, and spores 
are liberated. To sum up, in all these instances of sporulation, the yeast 
is functioning in the absence of nutriment, it then resolves itself into 
minute spores which, on being sown into malt wort or other favourable 
medium, reproduce yeast cells, which grow in the ordinary manner. It 
is interesting to notice that in Huxley and Martin's method, the yeast 
is exposed to air, and is in what Pasteur deems the fungus condition. 
Schiitzenberger asserts that the sporulation of yeast cannot occur with- 
out the presence of free oxygen. In Thorn's experiment he also pro- 
vides for free access of air by using no cover glass. The amount of air 
present must be very limited in the case of dough : probably under such 
circumstances, the act of sporulation goes no further than the premature 
breaking up of the cell wall, with the liberation of comparatively unde- 
veloped sporules, which, under favourable conditions, may develop into 
cells. Further investigation on this point is needed. 

231. Substances inimical to Alcoholic Fermentation — 

Dumas has carefully investigated the action of foreign substances on 
alcoholic fermentation ; Schiitzenberger quotes largely from his results ; 
the following data obtained by Dumas are taken from the English trans- 
lation of Schiitzenberger's work. In the first place, a series may be 
given of those bodies which retard, and when in sufficient quantity 
absolutely arrest, fermentation. These include the mineral acids and 
alkalies (phosphoric acid excepted), soluble silver, iron, copper, and 
lead salts ; free chlorine, bromine and iodine, alkaline sulphites, and 
bisulphites of the alkaline earths, manganese peroxide ; essences of 
mustard, lemon, and turpentine ; tannin, carbolic acid (phenol), creasote, 
salicylic acid ; sugar in excess, alcohol when its strength is over 20 per 
cent. ; and hydrocyanic and oxalic acids, even in small quantities. 
Phosphoric and arsenious acids are inactive. Sulphur has no effect on 
fermentation, but the carbon dioxide gas evolved contains from one to 
two per cent, of sulphuretted hydrogen. 

As may be gathered from the statement of the chemical changes 
produced by yeast, that substance gives always a more or less acid 
reaction. Dumas states that this acidity requires, for its neutralisation, 
alkali, equivalent to 0*003 grams of normal sulphuric acid per gram of 
yeast. In his experiments, he added various acids to yeast in proportions 
of from one to a hundred times the normal acid of the yeast. In this 



FERMENTATION. 115 



manner were determined the retarding or other action of the various 
acids on fermentation. Similar experiments were made with bases, and 
also salts; with the latter, saturated solutions were first made ; the yeast 
was allowed to soak in these for three days, and then its fermenting 
power tested by its action on pure sugar. Dumas divided the salts into 
four groups. First, those under whose influence the fermentation of 
the sugar is entire, and more or less rapid ; second, those which permit 
partial but more or less retarded fermentation ; third, those which per- 
mit the sugar to be more or less changed, but without fermentation ; 
fourth, those that prevent both change and fermentation. Alum is 
placed in the first of these classes, borax in the second, and sodium 
chloride (salt) in the third. Strychnine has no effect on the properties 
of yeast. For a detailed account of Dumas' results the student is 
referred to Schutzenberger's work. 

232. Low Yeast. — Sedimentary yeast, or the " low " variety of 
saccharomyces cerevinioe is that used in the manufacture of lager beer. 
In general properties it much resembles the high yeast which has already 
been studied. In form, the cells are somewhat smaller, and also rather 
more oval than those of normal high yeast ; but differ very little in 
shape from high yeast when grown, as at Burton, in very hard waters. 
Figure 8, paragraph 221, gives illustrations of low yeast. 

233. Distinctions between High and Low Yeast. — Whereas 

high yeast rises to the surface of the liquid during fermentation ; " low " 
yeast always falls to the bottom and forms a sediment there ; hence the 
name " sedimentary " yeast. Brewing with low yeast is performed at 
much lower temperatures than with high, thus, whereas with the latter 
pitching temperatures of 20° or 21° C. (68 or 70° F.) are employed; the 
lager beer brewer starts his fermentation at as low as 8° C (47° F.), or 
even 6° C. (43° F.) Working with this low temperature, fermentation 
proceeds much less rapidly than with high yeast ; growth and reproduc- 
tion proceed more slowly, and the budding gives rise to less extensive 
colonies of cells. As Pasteur aptly describes it, low yeast when grow- 
ing has a much less ramified appearance. It is doubtful whether the 
term " low," as applied to this yeast, has been given from the lowness of 
the temperature employed for fermentation, or because the yeast always 
drops to the bottom of the fermenting vat : both are characteristics of 
this variety. This yeast is further distinguished by its producing an 
inferior variety of beer to the celebrated product by high fermentation 
of English and Scotch breweries. 

234. Low Yeast not used for Bread -making.— An exceed- 
ingly prevalent error is, that the continental pressed yeasts now being 
so extensively employed in this country for bread-making are the pre- 
pared sedimentary yeast of lager beer. As a matter of fact, low yeast 
is very badly suited for the fermentation of bread ; its action is ex- 
tremely slow, and results in the production of a heavy, sodden, and 
frequently sour, loaf. Compressed yeasts are obtained from fermenta- 
tions for distilling and not for beer brewing purposes, and the yeast is 
invariably culled from the top of the fermenting liquid. 

235. Convertibility of Low and High Yeasts.— Students 



116 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

who approach this subject with a previous knowledge of the laws of the 
origin of species as a result of evolution, so ably enunciated and demon- 
strated by Darwin, will be prepared to expect from the general evidence 
of biology that not only high and low yeasts, but also all forms and 
species of saccharomyces have had one common origin, their diversities 
having been produced by differences in environment extending over 
numberless generations. When discussing, however, whether or not 
low and high yeast are convertible, and really therefore of the same 
species, it is understood that the question refers to convertibility during 
small amounts of time, not such lengthy periods as are requisite for an 
actual evolution of distinct species. Pasteur, as the result of personal 
investigations, believes that the two yeasts are distinct. This belief is 
founded on experiments in which high yeast was grown repeatedly at 
the lowest possible temperature, and low yeast at the temperature em- 
ployed for high fermentation. Supposing the yeasts to be pure at the 
commencement of such an experiment, he asserts that no transformation 
of the one variety into the other is effected. In this opinion he differs 
from many brewers, who state that under such conditions, the one yeast 
is converted into the other. Pasteur gives the following ingenious ex- 
planation of the observed change : if the high yeast had in it a few cells 
of low yeast as impurity, on being sown and caused to reproduce at a 
low temperature, the low yeast cells present would thrive well, while 
the high yeast would languish. The minute quantity of low yeast cells,, 
finding the conditions favourable to their growth, develop ; and the 
others, through the conditions being unfavourable, are after a time out- 
numbered and disappear. The change of low into high yeast is explained 
as being just the converse of that now described. Schiitzenberger,, 
however, states that, although with great difficulty, he is able by chang- 
ing the conditions of existence, to transform the one into another. 
Grove, in " Bacteria and Yeast Fungi," refers to Pasteur's view as to 
these being distinct species, but affirms his position to be untenable. 

The crucial point in all such investigations as these, is the purity or 
otherwise of the yeast used to commence the experiment : in all Pasteur's 
researches he used an apparatus which afforded most excellent means 
for the prevention of the incursion of foreign germs during his growth ; 
but he does not give us an absolutely certain method of obtaining a 
perfectly pure yeast to start with. In flasks of special construction,, 
well known as "Pasteur's Flasks" (for illustrations and descriptions see- 
his " Studies on Fermentation,") Pasteur introduces wort, then sterilises. 
the same by boiling it, and afterward sows therein a small quantity of 
the yeast he wishes to cultivate in the pure state. On the completion 
of this fermentation, a little of the new growth of yeast is taken and 
transferred with all due precautions to a second Pasteur's Flask of 
sterilised wort, and there again fermented. The yeast was grown in 
this way again and again, until the experimenter was of opinion that 
the preponderating growth of the yeast would have crowded out of ex- 
istence any foreign germs. To further aid in accomplishing this object, 
Pasteur also introduced in his growth flasks some substances inimical to 
the organisms he wished to exclude, or else worked at a temperature 
specially favourable to the particular organism whose growth he desired 



FERMENTATION. 117 



to favour. The yeast obtained in this manner he terms pure yeast ; 
undoubtedly this may be possible, and in many experiments was probably 
the case ; but it is nevertheless only a possibility we have to deal with, 
for the germs of foreign organisms may not be really dead, but only 
present in smaller quantity and in a weaker condition. More recent 
investigators have described methods by which it is possible to cultivate 
and develop the growth of yeast from one single isolated cell ; in this 
manner giving the surest guarantee of the actual purity of the yeast 
produced. 

Descriptions follow of methods for the absolute isolation of single 
organisms and their subsequent culture. The application of such 
methods to yeast would place beyond doubt the problem of convertibility, 
or otherwise, of high and low yeast. 

236. Method for the Isolation of Yeast and other 

Organisms. — Much still remains to be done in the way of isolating 
and examining in detail the functions of the different organisms that 
normally occur in bakers' yeasts. As such research will probably follow 
on the lines that have been adopted in other investigations having a 
similar object, the most authoritatively recognised methods will be 
described in detail. 

" Nsegeli's Dilution Method " is based on diluting down the liquid 
under examination until a single drop will, on the average, contain but 
one organism. This may be accomplished in the case of yeast by taking 
a drop of the mixture of yeast and water, diluting it down considerably 
with water previously sterilised by boiling, until the number of cells 
present in a drop can be counted under the microscope. If these are 
estimated, for instance, to be about one hundred, then this liquid is 
further diluted to an hundred times its volume. Every precaution 
must be taken to sterilise all vessels and liquids used in the operation. 
Each drop of this ultimate dilution of yeast should contain one cell 
only. Ten successive drops are then placed in ten separate tubes of 
-culture fluid, which may be sterilised wort. Some one or two will pro- 
bably remain unimpregnated, one or two others may have more than 
one form of organism present ; but the majority will contain but one 
growth only. The isolation of mixed organisms is thus effected. Han- 
sen, in his admirable researches on alcoholic ferments, adopted this 
method. To Koch is due the chief credit of bringing this method of 
investigation to its present comparative perfection. When one exa- 
mines samples of impure yeast, or still more, certain forms of putrefying 
matter, a multitude of different organisms may be detected. The 
problem of separating these from each other, and observing their action 
one by one, seems difficult, yet Nregeli's method just described shows its 
possibility. Koch, in his world-famed experiments on Bacteria (certain 
minute organisms to be hereafter described), used specially prepared 
gelatin as a cultivating medium. This material was mixed with water 
until it acquired such a consistency as to set, when cold, into a jelly, 
which became fluid at a temperature of 35° C. For a cultivation 
experiment some of the gelatin is melted, a few of the bacteria are taken 
out on the point of a needle and added to the gelatin. They are then 
diffused by shaking up the mixture, which is next poured out upon a 



118 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

flat surface properly protected. After some hours a separate and pure 
culture is obtained from each single bacterium present. On taking a 
minute particle from one of these little culture spots, and again sowing 
it in gelatin, a single species of bacterium was obtained. It was by 
experiments based on this principle, but carried out with most special 
precautions, that Koch isolated and exhaustively studied the " Comma 
Bacillus " of cholera, so inseparably associated with his name. 

But while bacteria are capable of functioning in this semi-solid gela- 
tin, yeast would find itself unable to do so : the author suggests the 
following slight modification of Koch's method for yeast investigation. 
Let a small quantity of the yeast under examination be mixed precisely 
as Koch directs with the gelatin, and pour the mixture out in a thin 
layer on the surface of a clean glass plate (a microscopic slide). Care- 
fully protect this until solid, then examine with the microscope until 
an isolated yeast cell is discovered of the kind which it is wished to 
further investigate. Cut the small piece of gelatin containing this one 
cell out, transfer it to another slide, examine again in order to see that 
it is the only one present, and then wash it into a flask containing steri- 
lised wort, there to develope and reproduce its kind. 

Lankaster most significantly writes — " It is only by such monosporovs 
cultivations, that we can arrive at solid conclusions in reference to the 
forms and activities of Bacteria, e.g., as to whether one form can give 
rise to progeny of another form, when its food and conditions of growth 
are changed, and again as to whether fermentative powers can be lost 
or acquired in the course of generations derived from one parent germ y 
but subjected to different conditions as to food, temperature, and oxy- 
gen. The method of gelatin cultivation devised by Dr. Koch places the 
means of following out these inquiries in the hands of every skilful 
microscopist." 

237. Pasteur's " New Bigh Yeast."— Pasteur relates that in 
1873, he accidentally met with a form of yeast that before was unknown 
to him. Its distinguishing characteristics were that in the mode of 
budding and size and shape of cells, it closely resembled the ordinary 
low yeast of lager beer, but differed in the essential particular that it 
rose to the surface during fermentation. He further speculates as to 
whether or not this variety of yeast is known commercially, and opines 
that it is. At the close of the Franco-German war in 1870, some 
Viennese traders established a factory near Paris for the manufacture of 
yeast for bakers. This yeast, Pasteur states to be a " high " one, differ- 
ing from the yeast of ordinary high fermentation, and closely resembling 
normal " low " yeast in microscopic appearance. He suggests the pro- 
bable identity of this yeast with his " new high yeast." The descrip- 
tion Pasteur gives of this yeast of Viennese origin accords closely with 
the well-known facts concerning the " French yeast " so largely imported 
for bakers' use in this country. 

238. SaCCharomyceS Minor. — This is a form of yeast described 
by Engel as being obtained by him from leaven (a name given to old 
dough). To obtain the ferment he washes a piece of leaven in the same 
way as described in a previous chapter for the separation of the gluten 



FERMENTATION. 119 



of flour from its starch. The yeast cells pass through, and may be 
detected by microscopic examination of the liquid after the larger starch 
cells have settled to the bottom. The cells of saccharomyces minor are 
globular, occurring either isolated or in pairs or groups of three. They 
are about 6 mkms. in diameter, and have an indistinct vacuole. In 
Pasteur's fluid they reproduce but slowly, and form new cells of the 
same dimensions as were the original. They easily reproduce by sporu- 
lation, the spores being about 3 mkms. in diameter, and are united in 
twos or threes. They, on the whole, closely resemble the yeast of beer. 
Although Engel treats saccharomyces minor as a distinct variety, the 
balance of evidence is in favour of its identity with 8. cerevUice. Grove 
considers it to be but a form of that ferment. The lesser size and 
activity may be attributed to its having continually reproduced itself 
in an unfavourable medium such as dough ; hence its stunted appear- 
ance and slow growth as compared with the more favourably environed 
yeast of beer. 

239. Saccharomyces EllipsOideilS. — This is the ordinary fer- 
ment of vinous fermentation, that is that by which must, or the 
expressed juice of the grape, is converted into wine. The cells of this 
variety of yeast are oval, and about 6 mkms. long, they reproduce both 
by budding and spores. When grown in malt wort, they produce a 
beer of a decided vinous flavour, which is sometimes made and sold as 
" barley wine." 

240. Saccharomyces Pastorianus. — The cells of this variety 

of yeast vary considerably in size ; they are cylindrical in shape, with 
oval ends, and appear when seen in colonies somewhat like strings of 
sausages. Budding occurs at the joints, where groups of smaller daughter 
cells may be observed ; these are first either round or slightly oval. The 
elongated cells are from 18 to 22 mkms. long, and about 4 mkms. in 
diameter ; the daughter cells are about 5 to 6 mkms. in length. 




fig. 9. — Saccharomyces Pastorianus. 
a, The same more highly magnified (after Pasteur). 

8. Pastorianus occurs in the after-fermentation of wine and beer, and 
also in baker's " patent" yeasts. As it is found in English beers which 
have been kept for some time in store, cells of it are probably more or 



120 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

less present in all commercial English yeasts. Being a less active 
variety than & cerevisia j , it remains dormant while the first or prin- 
cipal fermentation proceeds ; but when the most of the sugar has 
disappeared, the IS. paste nanus, being able to live and develop in a less 
nutritious medium, grows and reproduces. Brown and Morris point out 
that the dextrins cannot be either fermented or hydrolysed by ordinary 
yeast ; but that IS. padorlanus is capable of hydrolysing dextrin for 
itself, thus giving rise to an apparent direct fermentation of that body. 
This will explain how this latter ferment thrives and reproduces in a 
medium so deficient of sugar as not to permit the growth of saccharomyces 
cerevisice. 

241. Saccharomyces Mycoderma, or Mycoderma Vini.— 

Closely allied to the saccharomyces already described under the name of 
y r east is this species, which belongs to the fungus family proper. Saccharo- 
myces mycoderma requires for its growth and development free oxygen, 
and belongs to Pasteur's division of " aerobian " plants. Although yeast 
is capable of functioning in air, growing after the manner of a fungus, 
that is not, however, the normal method of development of yeast, whereas 
the fungi proper luxuriate rapidly when growing with free access to air ; 
but are speedily destroyed by enforced submergence below the surface 
of a liquid. Saccharomyces mycoderma occurs on the surface of wine, 
beer, and bakers' yeasts, on their being exposed for some days to the air, 
forming after a time a thick wrinkled skin or mycelium. Viewed 
under the microscope, the mycelium is found to consist of extending 
branches of elongated cells closely felted or intertwined together. The 
individual cells are either oval or cylindrical, with rounded ends. They 
are about 6-7 mkms. long, and 2-3 mkms. in diameter. The mycoderma 
vini reproduces either by budding or by spores. The spore forming cells 
attain a length of as much as 20 mkms. Home made or fermented 
ginger-beer readily permits the growth of this particular mould ; the 
so-called ginger-beer plant being largely composed of saccharomyces 
mycoderma. Particularly in summer time, the growth of this fungus 
proceeds with extreme celerity, the mycelium first formed being thrown 
into folds by its rapid development; at the same time considerable heat is 
produced. Microscopic examination shows that mycoderma vini is very 
like yeast in appearance, for a long time it was supposed that the two 
were identical, and that the mouldiness of beer was produced by the 
yeast cells ascending to the surface, and there developing as a fungoid 
growth. The two organisms are, however, distinct species, and have 
not been transformed one into the other. Mycoderma vini during its 
growth seizes oxygen with great avidity, entirely preventing, during the 
period of its actual life, the development of other organisms also re- 
quiring oxygen, but endowed with less vital energy. On submerging 
this mould during its active growth into malt wort, or other saccharine 
liquid, it for a short time causes fermentation, with the production of 
small quantities of alcohol ; but this action soon ceases with the early 
death of the fungus. In addition to this limited fermentative action, 
mycoderma vini acts on wines and beers as a somewhat powerful 
oxidising agent ; it conveys the oxygen of the air to the alcohol of the 
liquid, causing its complete slow combustion into carbon dioxide and 



FERMENTATION. 



121 



-water, and consequently rapidly lessening the alcoholic strength of the 
medium. Although wines and beers become sour simultaneously with 
-the development of mycoderma vim, the souring is not due to this 
organism, but to another distinct growth. 

The limited alcoholic fermentation produced by mycoderma vini leads 
-to its being classed among the aaccharomyces. 

242. Saccharomyces Albicans. — Except for its very close re- 
semblance in form to ordinary yeast, this species is scarcely of sufficient 
importance for mention. The cells are either round, oval, or cylindrical. 
Round cells are 4 mkms. in diameter ; oval, 3*5 to 5 mkms. long. It 
forms both spores and buds, the latter usually consisting of strings of 
cylindrical cells. This organism occurs on the mucous membrane of 
the mouth, causing the disease known as " thrush." It functions as a 
fungus, forming a mycelium, and when submerged sets up a very 
limited alcoholic fermentation. 




FIGURE 10. — Saccharomyces Albicans, 
beginning of growth ; b, further advanced ; c, formation of mycelium (after Grawitz). 



Experimental Work. 

243. Substances produced by Alcoholic Fermentation. — 

Prepare some ten or twelve ounces of malt wort, by mashing ground 
malt in five times its weight of water ; and take its density by a hydro- 
meter. To the wort add a small quanity of either brewer's or com- 
pressed yeast, place it in a flask arranged with a cork and leading tube, 
and set it in a warm place (30-35° C.) Attach the leading tube to a 
flask containing lime-water, so that any gas evolved by the yeast has to 
buble through the liquid. Notice that after a time fermentation sets 
in, and that the yeast rises to the top : gas bubbles through the lime- 
water and turns it milky, thus shewing that carbon dioxide is being 
evolved. When the liquid becomes quiescent through the cessation of 
fermentation; again, take its density with the hydrometer, notice that 
it is less than before ; return the liquid to the flask, and connect to a 
Liebig's condenser and distil ; notice that the first drops of the distillate 
have the appearance of tears, as described in paragraph 79, chapter III. 
Cease distilling when about one-tenth of the liquid has distilled over ; 
notice that the distillate has an alcoholic or spirituous odour. Test it 
for alcohol by the iodoform reaction. 

244. Microscopic Study. — Mount a few cells of yeast on a 
slide, with water, and examine with the eighth of an inch objective; notice 



122 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

the shape of the cells ; whether single or joined, whether the protoplasm 
is granular, and whether there are any vacuoles. Measure a few of the 
cells and carefully draw them to scale. Next mount a few cells in 
iodine solution, notice that this reagent produces no colouration ; any 
starch granules present will be stained blue. Next mount a few cells 
in magenta solution, and examine ; the interior contents are stained,, 
while the envelope remains uncoloured. Burst the cells by placing a 
few folds of blotting paper on the top of the cover, and then sharply 
pressing with the end of a penholder or pencil. Again examine, and 
note the empty colourless sacs, and crushed stained protoplasm. To 
prepare magenta solution, dissolve 1 part of crystallised magenta in 10 
parts of alcohol, and add 1600 parts of distilled water: 0*1 gram of 
magenta is a convenient quantity to take. 

Mount a trace of the yeast in a little warm malt wort, and examine 
carefully : notice alteration in appearance of the yeast cells as they set 
up fermentation : keep the microscope with slide in focus for some time 
in a warm place and observe from time to time the changes as they 
proceed. Watch specially for the development of budding, and as soon 
as any signs are detected watch the cell at short intervals until the bud 
has become completely detached from the parent cell. 

Sow a little yeast in a beaker in a small quantity of wort ; take out 
a little and examine under the microscope a few hours later : examine 
again on each successive day until some three or four days have elapsed 
since the fermentation has ceased. Note during the height of the fer- 
mentation the colonies of cells, sketch some of these : observe the clear 
outlines and transparent protoplasm of the new cells as compared with 
the shrunken appearance of the parent cells. As time proceeds, notice 
the gradual alteration in appearance of the yeast, until at last the new 
cells are similar in appearance to those originally sown. 

Cultivate some yeast on thin slices of potato, as described in para- 
graph 230, in order to observe the production of ascospores. 



LACTIC AND PUTREFACTIVE FERMENTATIONS. 12 3 



CHAPTER X. 

LACTIC AND PUTREFACTIVE FERMENTATIONS. 

245. SchizomyceteS. — Grove defines the Schizomycetes or "split- 
ting fungi " (Spaltpilze) as being unicellular plants, which multiply by 
repeated subdivision, and also frequently reproduce themselves by spores, 
which are formed endogenously. They live, either isolated or combined 
in various ways, in fluids and in living or dead organisms, in which 
they produce decompositions and fermentations, but never alcoholic 
fermentation. 

Among these organisms are included bacteria, bacilli, vibrios, &c, 
but comparatively few of these have an immediate bearing on the pre- 
sent subject, and so the great majority need not here be described. 

The Schizomycetes possess the property of surrounding themselves with 
a gelatinous substance, in which large colonies of them may be seen 
imbedded. They are then said to be in the "Zoogloea" stage. 

246. Bacteria. — These organisms consist of small cells, commonly 
cylindrical in shape ; they increase by transverse divisions of cells, and 
reproduce by sporulation. Bacteria have a spontaneous power of move- 
ment. 

247. Bacterium Termo. — This is essentially the ferment of 
putrefaction. Hay, meat, or flour infusions, malt wort and other 
liquids, on being exposed to the atmosphere, become turbid, and are then 
found on microscopic examination to be densely crowded with bacteria. 
The cells are oval in shape and about 1 *5 to 2 mkms. in length : they 
are constricted in the middle, giving them a sort of hour-glass appear- 
ance ; at each end is an extremely fine filament termed a " flagellum" 
and sometimes a "cilium." This is probably the organ by which the 
bacterium exerts its motile or moving power. 







fig: II.— -^Bacterium Termo. 
Z>, The zoogloea form (a and b, after Cohn, x 650 ; c, after Dallinger, x 4000) 



124 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

This definite movement of the bacterium must not be confounded 
with the simple oscillatory movement of small particles of matter when 
suspended in a fluid. This latter may be observed by rubbing up a 
little gamboge in water, and microscopically examining a drop of the 
liquid : the small solid particles are seen to be in a continual state of 
motion. This latter is termed the " Brownian " movement. 

The spores of the bacteria, in common with most other of those of the 
schizomycetes, are extremely tenacious of life. They may be dried up 
and exist in a dormant state for an indefinite time, without losing their 
vitality ; for immediately on being again moistened and placed in a 
suitable medium, they commence an active existence and cause putre- 
faction. The dry spores are not destroyed by even boiling them for. so 
long as a quarter of an hour ; they are also not affected by weak acids. 

248. Bacilli. — The word bacillus literally means a stick or rod, and 
is applied to the organisms of this genus because of their rod-like shape. 
The cells are long and cylindrical and occur attached to each other, thus 
forming rod-like filaments of considerable length. There is little or no 
constriction at the joints, which with low microscopic powers are scarcely 
observable. They increase by splitting transversely, and reproduce by 
spores. Bacteria and bacilli are closely allied genera, some species of 
the one closely resembling species of the other. In the very long cells 
of bacteria the transverse divisions may be detected, while in the equally 
long cells of bacilli no traces of division can be seen. Bacilli are some- 
times motile, but after a time pass into a condition of rest, or zoogloea 
stage. The long threads of bacilli often assume a zig-zag or bent form ; 
and unless subjected to very careful examination, appear to be continu- 
ous. Pasteur's filaments of turned beer " consist of baoilli." 

249. Bacillus Subtilis. — This organism is also termed " Vibrio 
subtil is : " the cells are cylindrical, and grow to about 6 mkms. in length, 
and are provided with a flagellum at either end. They usually occur 
adherent to each other, forming long filaments, as in figure 12. 




o o * -^^ 

figure 12. — Bacillus Subtilis, with spores (after Cohn). 
An enlarged illustration of B. subtilis is given in the following 
figure, 13 — 




FIG. 13.— Bacillus Subtilis, x 4000 (after Dallinger). 
They increase by transverse division, and reproduce by spores. As 



LACTIC AND PUTREFACTIVE FERMENTATIONS. 125 

the spore formation of B. subtllis has been most carefully observed, a 
description of its mode of reproduction will be of service as a type of 
that of the schizomycetes generally. In spore formation the protoplasmic 
contents of the cell accumulate at the one end, causing an enlargement 
there ; the rest of the cell after a time drops off and dies ; the mature 
spore may then live for even years without losing its vitality • and being 
of extreme minuteness, these spores permeate the atmosphere, and are 
ever ready to germinate on finding a suitable medium. In the act of 
germination the spore splits its membrane open, and a new rod grows 
and projects through the opening. Cohn states that B. subtilis causes 
butyric fermentation ; that is, a fermentation which produces butyric 
acid. Lister states that Bacterium lactis, the ferment which turns milk 
sour by the formation of lactic acid, closely resembles B. subtilis, and 
may possibly be identical with it. In case the latter supposition be 
correct, it follows that these organisms are capable of pleomorphism ; 
that is, that the one variety can exist as two distinct forms, and func- 
tioning differently, induce distinct types of fermentation. Van Tieghem 
states that butyric fermentation is produced by another bacillus, termed 
B. amylobacter, which view Frankland also adopts. B. amylobacter is 
morphologically very similar to B. subtilis, but is distinguished by con- 
taining, at times, starch within its cells. This latter organism always 
produces butyric acid, carbon dioxide, and hydrogen, whatever sub- 
stance it operates on. 

The term " vibrio" applied to certain forms of schizomycetes, is derived 
from their appearing to have a wriggling or undulatory motion ; this 
effect is illusory, being actually caused by their rotating on their long axis. 

250. Lactic Fermentation. — This is primarily the fermenta- 
tion by means of which milk becomes sour. The chemical change is a 
very simple one. Milk contains the variety of sugar known as lactose 
or sugar of milk, C 12 H 22 O n . By hydrolysis, this splits up into two 
molecules of a glucose called lactose, galactose or lacto-glucose, 
C 6 H 12 6 . When subjected to the influence of the lactic ferment, lacto- 
glucose is decomposed according to the following equation : — 
C 6 H 12 6 - 2HC 3 H 5 3 - 

Lacto-Glucose. Lactic Acid. 

Ordinary glucose is also susceptible of the same transformation. As 
previously stated, some doubt exists as to the exact place in the order of 
schizomycetes of the lactic ferment, as to whether it belongs to the 
bacteria or bacilli. It is always found present in greater or less quantity 
in commercial yeasts, also on the surface of malt ; in the latter case it 
may be detected by washing a few of the grains in water, and then ex- 
amining the liquid under the microscope. Its shape, according to Lister, 
when' developed in milk, is shown in the accompanying illustration : 




Fig. 14. — Bacterium Lactis x 1140 (after Lister) 



126 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

When viewed with a lower power in a field of yeast, it appears as small 
elongated cells somewhat constricted in the middle, generally detached, 
but occurring sometimes in twos and threes ; their length is about half 
that of an ordinary yeast cell. When single they exhibit the Brownian 
movement. 

Lactic fermentation proceeds most favourably at a temperature of 
about 35° C, and is retarded and practically arrested at a temperature 
which still permits the growth and development of the yeast organism 
and consequent alcoholic fermentation. For this reason brewers always 
take care to ferment their worts at a low temperature, thus preventing 
the lactic ferment, which is always more or less present, from any 
rapid development. The other bacterial and allied ferments are also 
affected in a similar manner by temperature. Dilute solutions of 
carbolic acid and also salicylic acid greatly retard lactic fermentation, 
while in such very weak solutions they have but little action on the 
yeast organism ; hence yeast is sometimes purified by being repeatedly 
grown in worts, to which small quantities of either of these acids have 
been added. The most favourable medium for lactic fermentation is a 
saccharine solution rather more dilute than that used for cultivating 
yeast, and containing albuminoids in an incipient stage of decomposition. 
The analogy between this fermentation and the alcoholic is close, 
because the two may proceed side by side in the same liquid. The 
presence of acid is inimical to lactic fermentation; hence the fermenta- 
tion arrests itself after a time by the development of lactic acid ; 
-provided this is neutralised from time to time by the addition of 
carbonate of lime or magnesia, the fermentation proceeds until the 
whole of the sugar has disappeared. In a slightly acid liquid, as for 
instance the juice of the grape, alcoholic fermentation proceeds almost 
alone ; but with wort, which is much more nearly neutral (if made with 
good malt), lactic fermentation sets in with readiness, and consequently 
has to be specially guarded against. 

In addition to its specific action on glucose, converting it into lactic 
acid, the lactic ferment has other functions of importance in commercial 
operations : thus, the presence of lactic ferment germs on malt, result in 
the formation of a little lactic acid during the mashing ; in distillers' 
mashes this is found to be somewhat valuable, and is encouraged, as it 
apparently helps to effect a more complete saccharification of the malt, 
and consequently increases the yield of alcohol. Distillers, therefore, 
frequently allow their malts to develop considerable acidity before using 
them, and give new mash tuns a coating of sour milk before bringing 
them into use. In bread making, by the Scotch system, the presence of 
the lactic ferment is deemed to make better bread : either the ferment, 
or the lactic acid produced, softens and renders the gluten of the flour 
more elastic. 

251. Diastasic action of Bacteria. — This latter action is a 

consequence of the property possessed by the bacteria of attacking albu- 
minoid bodies and converting them into peptones. Wortmann has de- 
voted considerable attention to (the investigation of the problem whether 
or not bacteria have any action on starch ; whether or not, by the 
secretion of a starch transforming substance similar to diastase, or in 



LACTIC AND PUTREFACTIVE FERMENTATIONS. 127 

any other but not clearly defined way, they are capable of transforming 
starch into soluble and diffusible compounds. In order if possible to 
obtain a solution of this problem, Wortmann experimented in the follow- 
ing manner : — 

To about 20 or 25 c.c. of water a mixture of inorganic salts (sodium 
chloride, magnesium sulphate, potassium nitrate, and acid ammonium 
phosphate, in equal proportions) was added to the extent of 1 per cent. 
The same quantity of solid wheat-starch was next added, and the liquid 
then inoculated with one or two drops of a strongly bacterial solution ; 
shaken, corked, and allowed to remain in a room at a temperature of 
18° to 22° C. (Bacterium termo was the predominating organism in 
the inoculating fluids employed.) In from five to seven days, the first 
.signs of commencing corrosion of the starch granules had become visible, 
the larger grains being first attacked, and much later, when these had 
almost completely disappeared, those of lesser size. 

In a second series of experiments, soluble starch was substituted for 
the solid form, the progress of the reaction being watched by the aid of 
iodine. Samples taken from time to time exhibited at first the blue 
•colour, then violet or dark red, passing to wine red, and finally, when 
the starch had disappeared, underwent no change. 

Wheat-starch grains are found to be by far the most readily attacked 
by bacteria when compared with other varieties, in several experiments 
having even completely disappeared before other sorts of starch were 
attacked. Of a number of starches, that of potatoes alone entirely 
resisted attack. When wheat-starch in the solid state was mixed with 
starch solution or with starch paste, the solution became entirely (and 
the paste in greater part) changed before any action occurred on the 
solid granules. 

With regard to this unequal power of resistance shown by different 
kinds of starch, Wortmann concludes from his further observations that 
the difference of rapidity with which a given kind is attacked and dis- 
solved by a ferment is inversely proportional to its density, provided 
always that the granules in question are entire and uninjured by cracks 
or fissures. In the same way are explained the differences in point of 
time in which granules of the same kind are sometimes observed so 
undergo change accordingly as they are intact or otherwise. 

The cause of potato-starch, or of bean-starch, and even under certain 
conditions, wheaten starch, resisting attack, in spite of the abundant 
presence of bacteria, is apparently to be sought for in the fact that 
other more easily accessible sources of carbon nutriment were also 
present, certain albuminoid constituents of the potato slices, or of the 
beans employed affording this more readily than the starch granules, 
just as in the experiments above cited, with wheaten starch solution 
and solid wheaten starch, the former was preferentially attacked ; only 
after all, or at least the chief portion, of the albuminoids present had 
been used up, was the starch in these cases attacked. 

Another point was also established in the course of these experiments 
— that if air is excluded, no appearances of corrosion or solution of the 
starch granules are manifested. 

That the starch in the process became changed in part to glucose was 



128 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

easily ascertained by testing with Fehling's solution, and a detailed 
series of experiments, made with a view to eliminating if possible the 
ferment itself, yielded evidence showing that bacteria possess the re- 
markable property of producing a starch-transforming ferment, only 
when no source of carbon other than starch is at their disposal, and 
this ferment is incapable of changing albumin into peptone, just as in 
the case of diastase. The results of Wortmann's researches may be 
briefly recapitulated — 

1 . Bacteria are capable of acting on starch, whether in the solid state,, 
as paste, or in solution, in a manner analogous to diastase. 

2. As in the case of diastase, different kinds of starch are attacked 
by bacteria with different degrees of rapidity. 

3. The action of bacteria on starch is manifested only in the absence 
of other sources of carbon nutriment, and when access of air is not pre- 
vented. 

4. The action of bacteria on starch is affected by a substance secreted 
by them, and which, like diastase, is soluble in water, but precipitable 
by alcohol. 

5. This substance acts precisely as diastase, in changing starch into 
a sugar capable of reducing cupric oxide, but is not possessed of pep- 
tonizing properties. 

These results of Wortmann's are quoted at some length because of 
their bearing on the action of bacteria in dough. One most important 
point is, that the diastasic action of bacteria, or their secretions, only 
occurs in the absence of albuminous matter, which is the substance most 
specially suited for the development of these organisms ; consequently, 
with the exception of the transformation of sugar more or less into lactic 
acid, the carbohydrates are unattacked by the schizomycetes during 
normal dough fermentation. The bacteria cause more or less change in 
albuminoids, but exert no diastasic action. These albuminoid changes 
are, by the way, unaccompanied by any appreciable evolution of gas. 

It will be noticed that Wortmann expressly states that the bacteria 
have no peptonising action ; while it is also as expressly stated that 
they readily attack the albuminoids. He does not state what substances 
he finds produced by this action. The opinion is, nevertheless, very 
generally held that peptones are produced during changes which occur 
during the fermentation of dough, and it has been supposed that the 
bacteria were the active agents. 

Even at the risk of tautology, it must again be stated that lactic fer- 
mentation cannot proceed without the intervention of the organism 
known as the lactic ferment, and that the yeast organism per se never 
produces the least trace of lactic acid. 

252. VISCOUS Fermentation. — Viscous fermentation is that 
variety which causes " ropy " beer. By means of an organism, consist- 
ing of globular cells of from 1*2 to 1*4 mkms. in diameter, adhering to- 
gether in long chains, glucose is converted into a peculiar sugar, or 
somewhat allied body, termed mannite, C 6 H 14 6 , and a gum similar to 
dextrin. On placing the viscous ferment into a saccharine liquid con- 
taining nitrogenous matter and the requisite mineral salts, viscous fer- 
mentation begins, and the liquid speedily becomes thick and sirupy.. 



LACTIC AND PUTREFACTIVE FERMENTATIONS. 129 

Beer, after having undergone this fermentation, runs from the tap in a 
thick stream ; and in very bad cases, a little when placed between the 
fingers, pulls out into strings. 

A somewhat similar condition sometimes holds in bread, which then 
is termed ropy bread ; it is probably due to the same cause. 

253. Butyric Fermentation. — At the close of the lactic fer- 
mentation of milk, the lactic acid or lactic salts, as the case may be, 
seem to be acted on by ferment organisms and converted into butyric 
acid with the evolution of carbon dioxide and hydrogen — 

2HC 3 H 5 3 = HC 4 H 7 2 + 2CO ? + 2H 2 

Lactic Acid. Butyric Acid. Carbon Dioxide. Hydrogen. 

As before mentioned, the ferment producing this change is either B. 
subtilis or B. amylobacter. The general conditions of butyric fermenta- 
tion are similar to those of lactic fermentation. A temperature of about 
40° C. (104° F.) is specially suitable; the presence of acids is to be 
avoided ; or where butyric fermentation is not wished, its prevention is 
more or less attained by working at a lower temperature and with a 
slightly acid liquid. However, with the fully developed organism, a 
slight acidity is unable to prevent butyric fermentation. Although 
butyric fermentation is usually preceded by lactic fermentation, it is 
possible that the butyric ferment may be capable of acting directly on 
the sugar itself. 

Tannin has a markedly prejudicial effect on the growth and develop- 
ment of bacterial life, hence the addition of this substance, or any com- 
pound containing it, to a fermenting liquid, exercises great preventive 
action on the development of lactic and butyric fermentation. Hops 
contain tannin as one of their constituents, and so a hopped wort is- 
much less liable to lactic fermentation than one unhopped. For a 
similar reason, bakers add hops to their patent yeast worts. 

254. Putrefactive Fermentation.— Putrefaction is that change 
by which most organic bodies containing nitrogen in an albuminoid 
form are first resolved into substances having a most putrid odour, and 
ultimately into inorganic products of oxidation. Bacterium termo has 
already been mentioned as the principal organism of putrefaction. 
Pasteur divides the act of putrefaction into two distinct stages, which 
it will be well here to describe. On exposing a putrescible liquid to the 
air, there forms on the surface a film composed of bacteria, <fcc; these 
completely exclude any oxygen from the liquid, by themselves rapidly 
absorbing that gas. Beneath, other more active organisms, which 
Pasteur groups together under the name of "vibrios," act as ferments 
on the albuminoid matters of the liquid, and decompose them into simpler 
products ; these simpler products are in their turn oxidised still further 
by the surface bacteria. Pasteur practically defines putrefaction, or 
putrid fermentation, as fermentation without oxygen. 

255. Action of Oxygen on Bacterial and Putrefactive 

Ferments. — Pasteur draws a hard and fast line between certain bacteria 
which he affirms live in oxygen, and absolutely require it, and others to 
which oxygen acts as a poison ; to which latter class he states that the 
vibrios belong. This name is used by him seemingly to refer to those 



130 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

micro-organisms which are in active motion. Of the bacteria of the 
first type, he mentions that if a drop full of these organisms be placed 
on a glass slide, and examined with a microscope, there is soon a ces- 
sation of motion in the centre of the drop, while those bacteria nearest 
the edges of the cover glass remain in active movement in consequence 
of the supply of air. On the other hand, if a drop of liquid containing 
the vibrios of putrefactive fermentation be studied in a similar way, 
motion at once ceases at the edge of the cover glass ; and, gradually, from 
the circumference to the centre, the penetration of atmospheric oxygen 
arrests the vitality of the vibrios. Pasteur thus divides the bacteria 
into an aerobian and an anserobian variety ; the former require oxygen, 
the latter find it a poison, and live and thrive best in its total absence. 
In proof of this view he describes experiments of a most careful charac- 
ter made by him. Schiitzenberger demurs to this opinion of Pasteur's, 
but says nothing as to the experimental evidence on which Pasteur's 
belief is based. Writes Schiitzenberger — " If fermentation is the result 
of such a need of oxygen, that the ferment takes it up from organic 
compounds, exciting their decomposition by a rupture of equilibrium, 
we cannot understand how oxygen can act as a poison to the ferment." 
But, although fermentation may be the result of a nutritive act in 
which decomposition is effected for the sake of oxygen, it does not 
necessarily follow that free oxygen can support the life of this particu- 
lar ferment. While plants can obtain their necessary carbon, hydrogen, 
and nitrogen, from inorganic compounds, animals, as previously stated, 
can only assimilate these elements from organic bodies. It may well be 
that the vibrio of putrefaction also finds itself unable to assimilate free 
oxygen, and can only nourish itself by the putrefactive decomposition 
of albuminoid and similar bodies. In fact, the conditions of life of this 
species are so different that some observers, among whom Roscoe may be 
cited, view the vibrio of putrefaction as an animal rather than as a 
plant. 

256. Conditions inimical to Putrefaction. — First and fore- 
most among these is the keeping out of the germs of putrefactive 
ferments from the substance. Meat and albuminoid bodies, generally, 
have come to be ordinarily viewed as very changeable substances, 
whereas in the absence of germ life they are very stable bodies. Putre- 
faction is the concomitant, not of death but of life. If animal fluids are 
drawn off into sterilised vessels without access of air they keep for an 
indefinite length of time. Or the germs may be destroyed by heat, 
when putrescible substances also remain unchanged. This latter is the 
basis of Appert's methods for the preservation of animal substances. 
These methods consist of exposing the substances to a sufficiently high 
temperature in hermetically sealed vessels ; or they may be heated in 
vessels so arranged that air may escape, but that any re-entering shall 
be freed from bacterial germs either by passing through a red hot tube, 
or by being filtered through a thick layer of cotton-wool. 

Tinned meats, milk, &c., are preserved on this principle of Appert's. 

Putrefaction may be arrested by intense cold, although even freezing 
bacteria does not destroy their power of inducing putrefaction when 
again warmed. As a consequence of this action of cold, meat when 



LACTIC AND PUTREFACTIVE FERMENTATIONS. 131 

thoroughly frozen may be preserved almost indefinitely. The absence 
of water is another preventative of putrefaction. Vegetables and meat, 
if thoroughly desiccated, show, on keeping, no signs of putrefying. In 
the same way, yeast, although in the moist state one of the most putres- 
cible substances known, may, by being carefully dried, be kept for 
months, not merely without putrefying, but also without destroying the 
life of the cell. 

257. Products Of Putrefaction. — These are exceedingly numer- 
ous and complex, among them may be found volatile fatty acids, butyric, 
and other of the series ; ammonia, and some of the compound or substi- 
tution ammonias ; ethylamine, trimethylamine, propylamine, &c. ; carbon 
dioxide, sulphuretted hydrogen, hydrogen, and nitrogen. 

258. Disease Ferments. — The ferments of lactic, viscous, and 
other than alcoholic fermentation, are frequently called " disease fer- 
ments," from their producing unhealthy or diseased fermentations in 
beer. 

259. Spontaneous Fermentation. — In this country, alcoholic 

fermentation is usually started by the addition of more or less yeast 
from a previous brewing ; it was formerly the custom to allow the fer 
mentation to start of itself. This is said still to be practised in some 
parts of Belgium in the manufacture of a variety of beer, known as 
" Faro " beer. In manufacturing such beers, the vats of wort are 
allowed to remain exposed to the air, and fermentation is excited by 
any germs of yeast that may find their way therein. It is possible that 
under such circumstances a wort may only be impregnated by yeast 
germs, in which case pure alcoholic fermentation alone will be set up. 
It is far more likely, however, that germs of lactic ferment and other 
organisms will also get into the wort ; consequently the beer will be 
hard or sour, and also likely to speedily become unsound. On the other 
hand, grape juice is always allowed to ferment spontaneously, but then 
this liquid is always distinctly acid, through the presence of potassium 
bitartrate ; and acidity retards or prevents bacterial fermentation. 

Bakers' barms or patent yeasts are at times allowed to ferment 
spontaneously ; they are then found to contain a large proportion of 
foreign organisms, principally the lactic ferment. Except where very 
special precautions are adopted, they are liable to be uncertain in their 
action, and often produce sour bread. 

But in all cases of so-called " spontaneous " fermentation it must be 
remembered that the fermentation is due to the presence in the wort of 
yeast cells or spores that either have been introduced along with the 
malt and hops without being destroyed, or else have found their way 
into the wort from some external source, such as germs floating in the 
air. It is also frequently possible that a sufficient quantity of yeast 
remains about the fermenting vessel from the last brewing to again 
start fermentation. 

Experimental Work. 

260. Prepare some malt wort ; filter and allow the liquid to remain 
for some days in an open flask. In about 24 hours the liquid becomes 



132 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

turbid ; examine a drop under the microscope with the highest power at 
disposal. Bacteria will be seen in abundance ; notice that they have a 
distinct migratory movement. Examine a sample each day, and observe 
that the bacteria grow less active, and ultimately become motionless ; 
they have then assumed the zooglcea stage. Carefully search the liquid 
for other organisms ; bacilli should be detected, being recognised by 
their filamentous appearance. Vibrios should also be observed ; they 
appear very like bacilli, except that they have bent joints. "When 
actively moving they exhibit an undulatory movement, depending on 
their rotation on their long axis. 

Examine microscopically some of the sediment of " turned " beer ; 
large quantities of bacilli can usually be observed. These organisms 
are also commonly found in bakers' patent yeasts. 

Place some fresh clear wort in a flask and plug the neck moderately 
tightly with cotton wool ; boil the liquid for five minutes and allow to 
cool : notice that the contents of the flask remain clear. At the end of 
a week, remove the plug and examine a drop of the liquid under the 
microscope, bacteria and other organisms are absent. The wort is still 
sweet and free from putrefactive odour. Let the flask now stand freely 
open to the atmosphere : organic germs gain entrance, and putrefactive 
or other changes rapidly occur. On the next and succeeding days, ex- 
amine microscopically. 

Procure a small quantity of milk and allow it to become sour ; ex- 
amine microscopically for bacterium lactis. Also, wash a few grains of 
malt in a very little water, and examine the washings for this organism. 

Prepare two samples of wort, strongly hop the one by adding hops in 
the proportion of one-tenth the malt used : boil the two samples, filter, 
and set aside under precisely the same conditions. Observe the relative 
rate of growth and development of bacterial life in the two. 



TECHNICAL RESEARCHES ON FERMENTATION. 133 



CHAPTER XI. 

TECHNICAL RESEARCHES ON FERMENTATION. 

261. The author has now for some time past been engaged on a 
series of experimental researches which have had as their object the 
clearing up of points on fermentation as related to bread making, and 
also the furnishing of trustworthy data as to the effect on yeast of vari- 
ations in the conditions to which it is subjected during panary fermen- 
tation. He takes this opportunity of laying his results before the 
public for the first time. Those readers who have carefully studied the 
preceding chapters, and who have also kept themselves au courant with 
scientific articles and discussions on the subject in the trade journals, 
will immediately see the object of many of the experiments : the reason 
for others will appear later. 

262. Strength Of Yeast. — To the baker, the first consideration 
about yeast is its strength or gas yielding power : there are other effects 
which it also produces, but its all-round activity may be fairly measured 
by the quantity of gas it evolves from a suitable saccharine medium. 
The term " strength " is therefore used in this sense ; it follows that the 
strongest yeast will also raise bread better, because the rising of the dough 
is due to the gas evolved by the yeast from the saccharine constituents of 
the flour. Different modes have been adopted from time to time for 
the purpose of testing the strength of yeast. The essential principle of 
these has been to ferment a definite quantity of some saccharine fluid 
with a constant weight of yeast, at a constant temperature, and to then 
determine the volume of gas evolved in a given time. Meissl, of 
Vienna, uses the following process, which, like most others of its kind, 
is based on the principle that the strength of the yeast can be judged 
from the amount of carbon dioxide it produces from a certain quantity 
of sugar, the other substances being in equal proportions. 

In order to carry out the experiment by this process, the following 
substances must be prepared by rubbing them together : 400 grams of 
refined cane sugar, 25 grams of phosphate of ammonium, and 25 grams of 
phosphate of potassium. A small vessel should be ready at hand of 70 
to 80 c.c. capacity, and fitted with an india-rubber stopper containing 
two holes, in one of which should be placed a bent glass tube, the long 
end of which should nearly reach the bottom of the vessel, and the top 
end, during the fermentation, should be corked up. The second hole 
serves for the reception of a small chloride of calcium tube. 

The testing of the yeast must now be commenced in the following 
manner : 4*5 grams of the above mixture must be stirred gently, and 
dissolved in 50 c.c. of drinking water. In this liquid 1 gram of the 



134 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

yeast on which the experiment is to be tried should be carefully stirred 
and mixed until no lumps are to be seen. The vessel with its contents 
must be weighed and then placed in water at a temperature of 30° C, and 
left to remain during six hours. At the end of this time it must be taken 
out and plunged immediately into cold water in order to cool it as 
quickly as possible. The stopper is then taken out of the bent glass tube, 
and the air allowed to enter during a minute or two, so as to drive out 
the carbon dioxide. The vessel and its contents must then be weighed. 
The loss of weight arises from the quantity of carbon dioxide which has 
been thrown off during the process. By this method, the carbon dioxide 
is estimated by weight : the chloride of calcium tube is affixed for the 
purpose of retaining any traces of aqueous vapour which otherwise would 
escape. 

During the summer of 1884 the author made some experiments by 
this method, using the form of apparatus described above. The follow- 
ing table gives the results obtained ; the weights being in grams. At 
the close of the experiment in each case the acidity was determined and 
calculated as lactic acid : — 



TECHNICAL RESEARCHES ON FERMENTATION. 



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In many ways this apparatus and method were susceptible of improve- 
ment, at least when used for technical and commercial purposes. In 
the first place the actual weight of the flask with contents amounted to 
some 80 or 90 grams, while the weight of carbon dioxide evolved varied 
from 0-291 to 1*237 grams. To accurately measure these differences of 
weight in an apparatus, itself weighing so much, a very delicate balance 



136 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



is requisite. This method is capable, in competent hands, of yielding 
accurate results ; but it is tedious, and does not give all the information 
that could be wished. 

Another mode of procedure is to collect the gas in a jar over mercury 
in a pneumatic trough; this undoubtedly gives the most accurate results, 
but is open to the objection that mercury is expensive, and the apparatus, 
from its great weight, heavy and cumbersome. The reader is already 
aware that water is capable of dissolving carbon dioxide gas to the ex- 
tent of its own volume ; this, therefore, is an obstacle to the employ- 
ment of water for its collection. The writer, nevertheless, made the 
experiment, and found that on collecting the gas, evolved by the yeast 
during fermentation, in the ordinary manner in a graduated gas jar over 
water, most interesting results could be obtained. These were of course 
not absolutely correct, because a certain quantity of the gas was absorbed 
by the water ; still, duplicate experiments gave corresponding quantities of 
gas, while most important information was gained as to the general char- 
acter of different yeasts when examined in this manner. Results obtained 
in this way may therefore be viewed as comparable with each other. 

263. Yeast Testing Apparatus. — In the next place a series of 
experiments were made in which the gas was admitted to the graduated 
jar through the top, and so did not bubble through the water at all. 
When collected in this way the amount of absorption was small and 
very uniform. Two jars were two-thirds filled in this manner with 
washed carbon dioxide gas prepared from marble and hydrochloric acid. 
They were then allowed to stand, and the amount of absorption observed 
hourly. The rate of absorption, with the particular jars used, was 
as nearly as possible a cubic inch per hour. Subsequent trials with jars 
of one hundred cubic inch capacity gave an outside rate of absorption 
of two cubic inches per hour. As a result of numerous experiments, 
the writer now employs the form of apparatus figured below : 

e d 



f 



liiiiiiiiiiiiniini i i i T m 



ff 




^ 5 

-4- io 



4 85 

4- jo 



/ 



Z3 



m. 



as 



£Stf* rr u 



FIG. 15. — YEAST TESTING APPARATUS. 



TECHNICAL RESEARCHES ON FERMENTATION. 137 

The glass bottle, marked a in the figure, is of about 12 ounces capacity, 
and is fitted with india-rubber cork and leading tube, b. The sugar or 
other saccharine mixture to be fermented is raised to the desired tem- 
perature, and then placed in this bottle. The yeast is weighed out, and 
then also added ; they are then thoroughly mixed by gentle agitation. 
By means of an india-rubber tubing joint at c, the generating bottle is 
connected to the leading tube e of the glass jar /. This leading tube is 
provided at d with a branch tube, which may be opened or closed by 
means of a stopper of glass rod and piece of india-rubber tubing. The 
jar /is graduated, as shown, into cubic inches, commencing immediately 
below the shoulder with 0, and ending near the bottom with 100. 
This constitutes the apparatus proper * in use the generating bottle a is 
placed in a water bath, g g. This bath is fixed on a tripod over a 
bunsen burner, and is provided with an iron grid, h, in order to prevent 
the generating bottle coming in absolute contact with the bottom of the 
bath. By means of an automatic regulator the bath is maintained at 
any desired temperature. The gas jar/ stands in a pneumatic trough, i i. 

As a rule more than one test is made at a time, the water-bath should 
therefore be sufficiently large to take four or six bottles at once ; two 
pneumatic troughs are then employed, and either two or three of the 
gas jars / arranged in each. "While for strictly accurate experiments it 
is essential that the yeast bottles be kept as nearly as possible at a 
definite temperature, yet results of interest may be obtained without 
the employment of a water-bath. The whole apparatus should, under 
those circumstances, be placed in some situation where, as nearly as 
possible, a constant temperature is maintained. 

At the start of the experiment the air is exhausted through d, which 
is again closed with the stopper. As the fermentation goes on the gas 
evolved is collected in /, and its volume read off, from the surface of the 
water, at the end of each half-hour or hour. Full and detailed particu- 
lars are given at the end of this chapter as to the exact mode of 
procedure in using this apparatus. 

When the requisite allowance is made for the absorption of the gas 
by water, the corrected reading very nearly corresponds with the 
absolute amount of gas which has been evolved. There are slight 
variations due to alterations of barometric pressure and of temperature ; 
these can, if wished, be calculated out and allowed for — that is not, 
however, for ordinary purposes necessary. Gases are usually measured 
at a standard pressure of 760 millimetres, or very nearly 30 inches of 
mercury, that is with the barometer standing at 30. A rise or fall of 
the barometer through half an inch only makes a difference of one- 
sixtieth on the total reading, and this may as a rule be neglected. In 
case the estimation is being made in either the laboratory or a bake- 
house, the temperature is, as a rule, fairly constant. Supposing it be 
taken at 70° F., then it will be found that a difference of 5° either way 
only causes a variation in the volume of the gas of one hundredth the 
total amount. Barometric and thermometric variations may therefore, 
for most practical purposes, be neglected. Further, whatever variations 
there may be either in temperature or pressure, all the tests made at 
the same are made under precisely similar conditions. 



138 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



The corrections for absorption are not made in the following readings, 
because it is evident that at the outset the carbon dioxide remains as a 
layer of gas within the bottle, simply displaying air over into / ; during 
this time no absorption can take place. It should, however, be re- 
membered that when the gas remains stationary for any length of time, 
a quantity must have been evolved about equal to that being absorbed. 

264. Degree of Accuracy of Method.— This is a matter of 

great importance, because unless fairly constant and accurate results 
are obtainable, little or no confidence can be placed in them, or any 
deductions based thereon. A number of duplicate experiments were 
therefore first made in order to test the accuracy of the estimations ; 
the results are appended : — 

No. 1. Brewers' Yeast, \ oz. ; Sugar Mixture, \ oz. ; "Water, 6oz. at 
30° C. 

No. 2. Duplicate of No. 1. 

No. 3. French Compressed Yeast, \ oz. ; Sugar Mixture, \ oz. ; 
Water, 6 oz. at 30° C. 

No. 4. Duplicate of No. 3. 



Time. 


Gas Evolved in Cubic Inches. 


Temperature. 


No. i. 


No. 2. 


No. 3. 


No. 4. 




\ hour 

1 „ ... 

i^ hours ... 

2 „ ... 

2i „ ... 

3 »» - 

35 ».» - 

4 ,. -. 

4k ., ••- 

5 ,. - 

sh „ -. 

6 „ ... 


O'O . 

7 
07 

< 5 ' 8 

6-5 

14-2 ■» 

7-8 

22'0 ( 

8-o 

3 0-0 I 

£ 11*0 

41 'o\ 

6-o 
47 -o 

7-5 
54*5 ' 


O'O . 

o' 5 
o-5 

* < 5 ' 5 
6-o * 

. 7 ' 8 

8-2 
22 -o : 

77 
297 

"•3 

410 

57 
467 

8-o 

537' 


O'O^ 

,,} yl 

3 M 
V161 

V21'8 

4i*o< 

>21'0 

62 -o< 

>20'0 

82 -o{ 

h21'5 

i°3'5< 

V22-3 

i25'8{ 

}i 7 -8 
i43 - 6< 

M4'9 
i58'5< 

I 9'5 
i63-o^ 

\ 7"o 

} 2-8 


O'O^ 

} 2-5 
i77{ 

V21'4 

39'i< 

[207 
59'8{ 

f20'4 

80-2^ 

>2rO 
IOP2< 

I24'4< 

V2o-4 
I44'8< 

* r 5 ' 9 

i6o7< 

} 9*3 
170-0^ 

} 5'o 
i75'°< 

} o-8 

i75'8 J 


297 
30'0 
30*0 
29'8 
28-9 

29*5 
30-0 

30-25 
30-25 
30-0 
30-0 

30 'O 

29-9 






The figures placed opposite the brackets represent the volume of gas 
given off in each successive half hour. A thermometer was placed in 
the water-bath and the temperature observed at the time of each read- 



TECHNICAL RESEARCHES ON FERMENTATION. 



139 



ing, and registered in the last column. The temperature in this experi- 
ment shows considerably greater variations than that in those made later. 
It will be noticed that the both pairs of duplicates agree very closely 
throughout the entire fermentation. 

It may here be mentioned that a half ounce of sugar yields, on the 
supposition that the whole is transformed into carbon dioxide and 
alcohol, the following quantities : — 

\ oz. of sugar = 14/2 grams, and yields 7 '30 grams of C0 2 = 
3-705 litres = 226 cubic inches at 0° C. = 

242 „ 20° C. 

(One cubic inch = 16*4 c.c.) 
It will be remembered that actually only about 95 per cent, of the 
sugar is thus converted into carbon dioxide and alcohol ; these quantities 
in strictness, therefore, require to be reduced about 5 per cent. 

265. Constancy of Strength of same Yeast.— In many of 

the following experiments yeast of the same brand was used, though on 
different days ; it is a matter, therefore, of some importance to know 
the extent of variation found on yeast of the one brand at different 
times. One brand of yeast (Yandermin's " Cream " ) gave the following 
results : — 

No. 1. — April 27th, 1885,] Cream yeast \ oz., sugar mixture, 
No. 2.— May 7th, 1885, \ \ oz., water, 6 oz. at 30° C. 
No. 3.— June 30th, 1885, J 



Time. 


Gas Evolved in Cubic Inches. 


No. i. 


No. 2. 


No. 3. 




1 hour 

2 hours 

3 >. .-•■ ~ 

4 .» 

5 » 

6 „ 


O'O, 

V2I7 

2i'7< 

A I 41 ' 3 

63-0^ 
« ) 33 *° 

96 -o^ 

f34*3 
i30'3^ 

V2 4 -2 

I54'5^ 

M57 
170*2-' 


0*0. 

[24-5 

24*5< 

136-4 
60-9^ 

M3'i 
i04*o< 

i36*o< 

[22-5 

i75'o J 


0*0 1 

287 
287 

3* '9 
6o-6 

43*6 
104-2 j 

40-8 

I75 '°l 
V 2-8 

177-8^ 



Although these results do not agree with that closeness observable in 
the duplicates, yet it will be seen that the yeast is throughout fairly 
similar in behaviour ; still, it must be remembered that in experiments 
made on different days the results are not always strictly comparable, 
because the yeast is sure to be not absolutely the same in each case. 

266. Effect of different Media on Yeast Growth.— That 

certain substances are eminently fitted for aiding the growth and de- 
velopment of yeast while others are not so suited has already been 



HO 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



stated. In order to measure quantitatively the effect of sowing yeast in 
different solutions, the following determinations were made. 

267. Comparison between Sugar, " Yeast Mixture," 

Pepsin, and Albumin. — The " yeast mixture " referred to is based 
on the fluid in which Pasteur cultivated yeast, and which is known as 
" Pasteur's Fluid." Pasteur employed a solution of sugar and am- 
monium tartrate to supply saccharine matter and nitrogen ; to this he 
added some yeast ash as a source of mineral constituents. This fluid 
may be closely imitated by use of the following formula — 

Potassium Phosphate ... ... ... 20 parts. 

Calcium Phosphate 



Magnesium Sulphate 
Ammonium Tartrate 
Purest Cane Sugar 
Water 



2 

2 

100 

1500 

8376 



10,000 parts. 
As this solution keeps badly, the yeast mixture consists of Pasteur's 
Fluid, minus the water. The salts are first powdered and dried, and 
then mixed until thoroughly incorporated. This mixture has the great 
advantage that while dry it can be kept any length of time without 
change. 

Date, 26th April, 1885. 
No. 1. Pure sugar, \ oz. (14-2 grams) ; compressed yeast, \ oz, 

(3*5 grams) ; water, 6 oz. (170 grams) at 30° C. 
No. 2. Yeast mixture, \ oz. ; compressed yeast, \ oz. ; water, 6 oz. at 

30° C. 
No. 3. Pure sugar, \ oz. ; pepsin, 1 -5 grams ; compressed yeast, J oz. ; 

water, 6 oz. at 30° C. 
No. 4. Yeast mixture, J oz. ; pepsin, 1 *5 grams ; compressed yeast, 
\ oz. ; water, 6 oz. at 30° C. 



TECHNICAL RESEARCHES ON FERMENTATION. 



HI 



Time. 



l\ hours 
2 

3 

3i 

4 

41 

5 

Sk 

6 

6* 
7 

7£ 
8 

84 
9 



No. i. 



io-8 



59"5 



3"5 



Gas Evolved in Cubic Inches. 



No. 2. 



•28 -o 



No. 3. 



24' 



28 -o 



No. 



I05'2 
I2I-8 

139-2 
153-6 



i6-6 



17-4 



w 



27-9 



On the next day, a second series of experiments were made, which 

were exactly the same as the first in all particulars, except that a 

quarter instead of an eighth of an ounce of yeast was employed in each 

case. The results follow as before : — 

Date, 27th April, 1885. 

No. 1. Pure sugar, J oz. ; compressed yeast, J oz. j water, 6 oz. at 

30° C. 
No. 2. Yeast mixture, \ oz. ; compressed yeast, \ oz. ; water, 6 oz. at 

30° C. 
No. 3. Pure sugar, J oz. ; pepsin, 1*5 grams \ compressed yeast, \ oz. \ 

water, 6 oz. at 30° C. 
No. 4. Yeast mixture, \ oz. j pepsin, 1*5 grams; compressed yeast, 
J oz. ; water, 6 oz. at 30° C. 



142 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



Timb. 



O 

£ hour 

I >, 

I I hours 

2 

2\ 



4 

4h 

5 

5* 

6 

6£ 
7 



9 

91 

io 

10* 



Gas Evolved in Cubic Inches. 




No. 3. 



179*5 



10*2 



10 -o 



9'3 



93 



1 22'3 

.1-6 { 

^24-4 

5 6-o 

^26'0 



8 2 -o 



24 '9 



106-9 , 

[27-6 



I 34'5 
i57-o 
I74-4 
186-3 
191-6 
193 "5 
193-5 



j-22-« 

}i7"4 
j-n-9 

} 5 '3 

j- O'O 



In these experiments an anomaly will be noticed in the systems of 
weights employed. In deference to the fact that many of the readers 
of this book will be much more familiar with the English than the 
metric weights and measures, the writer has, where practicable, used 
the former system ; although were he to follow his own predilections, 
all quantities would throughout have been expressed in grams and cubic 
centimetres. 



TECHNICAL RESEARCHES ON FERMENTATION. 



143 



The relation between grams and fractions of an ounce may be under- 
stood by remembering once for all that 
1 ounce or 16 drams = 

2 33 35 ^ 33 = 

1 4 _ 

4 35 55 ^ 33 — 

C 11 1 1 •" 11 == 



28-35 


grams. 


14-2 




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Fig. 16. 
In order to render these tabulated results more clear they have been 
set out diagrammatically. The numbers along the bottom of the dia- 
gram, Figure 16, represent the hours at which the readings were taken: 
those arranged vertically up the sides show the number of cubic inches 
of gas. The first or left hand series of results are those obtained with 
\ oz. of yeast. Take No. 1 of this series as an illustration of how these 
lines are set out; at the end of one hour, 3 -9 cubic inches of gas had 
been evolved ; therefore on the vertical line, with 1 at its base, a mark 
was made at a distance of 3 -9 up the line, reckoning the distance be- 
tween each two horizontal lines as 10. At the end of the second hour 
12*0 cubic inches had been evolved, and so, on line 2 a mark is made at 
the 12 cubic inch mark ; at three hours the gas registered 20 '6 cubic 
inches, and accordingly a mark is made on line 3 at 20'6 cubic inches. 
These marks are continued for every reading taken. They are then 
joined together with the production of such a line as that marked 1 in 
the diagram. If these readings were taken at very short intervals, say 
of five minutes, and such a diagram constructed with a vertical line for 
every five minutes, the line produced by connecting up each reading 
would give a fairly smooth curve. Remember, that a curve may be 



144 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

said to be made up of an infinite number of infinitely short straight 
lines placed end to end (a circle is sometimes called an infinite polygon.) 
The actual lines in the diagram approach to such curves, and are com- 
monly spoken of as " curves," although made up of short straight lines. 
The present and similar diagrams may be said to represent the curves 
showing the relation between the quantity of gas a yeast evolves and 
the time it takes in so doing. The more rapid the evolution of gas, the 
more nearly does the curved line approach the vertical, while when no 
gas is being evolved, the curve becomes horizontal. During the time 
that the speed at which gas is being evolved increases, hour by hour, the 
curve bends upwards ; while the gas is coming off with absolute uni- 
formity of speed, the curve becomes a straight line ; when the speed at 
which the gas is being evolved decreases, the curve bends downwards. 
The object of these curves is to enable a comparison to be made at 
sight between the results of a number of experiments. When it is 
desired to read very accurately the exact quantity of gas given off at 
any particular time, the tables should be consulted. 

Studying first the results with one-eighth of an ounce of yeast, in 
No. 1 with pure sugar the gas is evolved slowly, but with considerable 
constancy : this is shown by the curve being almost a straight line. 
Compared with the sugar, the yeast mixture, No. 2, induces a much 
more rapid evolution of gas : but little is evolved during the first hour, 
but after that the evolution proceeds at a tolerably uniform rate of about 
10 cubic inches per half -hour : towards the end the speed begins to fall 
off. Throughout the experiment, the quantity of gas evolved is at each 
reading more than double that with sugar. In the next place, a mix- 
ture of sugar and pepsin, No. 3, was tried : with this the quantity of 
gas evolved during the first hour was very low, 2*3, but during the 
second hour the production increases over that of pure sugar, and con- 
sequently curve 3 crosses over curve 1. No. 3 then proceeds uniformly, 
but with an average of about 20 cubic inches behind No. 2 : toward 
the end it begins to fall off, but only slightly ; in two or three hours' 
time No. 3 would probably have crossed No. 2. The whole of these 
three were still actively evolving gas at the taking of the last reading. 
In No. 4, pepsin was added to yeast mixture ; in this the evolution of 
gas was most rapid of all • from the start right on it keeps well in 
advance of the others : at first with each reading the speed increases, 
but at the end it falls off, and at last entirely ceases, having caused in 
eight hours the evolution of 184*5 cubic inches of gas, the correction 
for absorption being neglected. 

Practically the same effects are observed with the quarter-ounce tests 
as were obtained in the eighth of an ounce experiments. The evolution 
of gas was in each case very uniform, at first a slight increase and 
afterward a regular falling off. No. 1 is again the lowest, but shows 
that at the last reading gas was still rapidly coming off. Nos. 2 and 4 
again occupy very nearly the same relative position to each other, but 
in this experiment No. 2 is exhausted at the end of the eighth hour, 
while No. 4 ceases to evolve gas after six hours. No. 3 again starts 
slowly, and only in the third hour overtakes No. 1, but at the end of 
seven hours it has also overtaken and passed No. 2, giving at the end 



TECHNICAL RESEARCHES ON FERMENTATION. 145 

of ten and a half hours a reading of 211 '5 cubic inches. The effect of 
the greater quantity of yeast was in each case to hasten fermentation * 
this will again be referred to when dealing specially with the question 
of quantity. 

In order to test whether the pepsin itself gave off gas, 1 *5 grams of it 
were taken and mixed with water and yeast, as in the preceding experi- 
ments : no gas, however, was evolved. A further experiment was 
made in a similar fashion with white of egg, but no gas was produced. 
As a third test, 15 grams of white of egg were mixed with 6 oz. of 2 "5 
per cent, salt solution at 25° C, and then one quarter ounce of yeast 
added. At the end of ten hours, 1 "3 cubic inches of gas were evolved, 
which quantity had increased in twenty-two hours to 1*5 cubic inches ; 
this is practically equivalent to the non-production of gas. 

From these experiments the following conclusions are derived : — 

Pure sugar undergoes a regular but somewhat slow fer- 
mentation. 

Sugar mixed with about ten per cent, of pepsin ferments at 
first more slowly, but afterwards much more rapidly. 

" Yeast mixture," consisting of sugar, ammonium tartrate, 
and inorganic salts, ferments from the commencement still 
more rapidly. 

Yeast mixture, with about ten per cent, of pepsin, undergoes 
still more rapid fermentation. 

Nitrogenous bodies alone, as pepsin, albumin, in water, or 
2£ per cent, salt solution, evolve practically no gas. 

Pepsin and other nitrogenous bodies must therefore be considered, 
not as the substances from which yeast causes the evolution of gas, but 
as stimulating nitrogenous yeast foods. 

268. Comparison between Filtered Flour Infusion, 
Wort, and Yeast Mixture Solution. — Pursuing the same line of 

investigation, experiments were next made for the purpose of examining 
and comparing flour infusion, wort, and yeast mixture, as fermentable 
substances. An infusion of flour was made by taking 400 grams of 
flour, and 1000 c.c. of water, these were shaken thoroughly in a flask, 
from time to time, for half-an-hour, and then allowed to subside : the 
clear liquid was filtered, and its specific gravity taken ; this amounted 
to 1007*2. Meantime, some malt wort had been prepared ; this was 
divided into two portions, the one of which was boiled, the other allowed 
to remain at the mashing heat. These were next cooled, and each 
diluted down until the specific gravity coincided with that of the flour 
infusion. A solution of yeast mixture of the same density was also 
prepared. Permentation was started in each of these with the results 
given in the following table, and illustrated in the left hand series of 
the accompanying diagram, Pig. 1 7. It should be noticed that in this 
diagram the vertical scale is different to that in the last • the space 
between each two lines is equal to two instead of ten cubic inches. 

Date, 8th May, 1885. 
No. 1. 40 per cent, filtered flour infusion, Sp. G. 1007*2, 6 oz. at 
30° C. ; compressed yeast, \ oz. 



146 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



No. 2. Unboiled malt wort, Sp. G. 1007*2, 6 oz. at 30° C. ; com- 
pressed yeast, J oz. 

No. 3. Boiled wort, Sp. G. 1007*2, 6 oz. at 30° C. ; compressed yeast, 
i oz. 

No. 4. Yeast mixture and water, Sp. G. 1007*2, 6 oz. at 30° C. ; com- 
pressed yeast, \ oz. 



Time. 


Gas Evolved in Cubic Inxhes. 


Temperature. 


No. t. 

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Fig. 17. 

The flour infusion evolved gas but slowly, and toward the end of five 
hours over which the experiment lasted, had fallen off considerably. 
The two malt infusions yielded carbon dioxide at about double the 
speed ■ that in the boiled wort being the higher. The greater quantity 
of gas in the latter instance is due to the fact that boiling coagulates 
some of the albuminoids of the wort, and so leaves a greater percentage 
of sugar in the liquid, when both are diluted to the same density. This 
is an interesting instance of the removal of albuminoids resulting in a 
more copious and rapid evolution of gas. The yeast mixture causes the 



TECHNICAL RESEARCHES ON FERMENTATION. 147 

carbon dioxide to be evolved with still greater rapidity. Summing up 
the results — 

In solutions of the same density, 

Flour infusion, on fermentation, yields gas somewhat slowly; 

Unboiled wort, at about double the speed ; 

Boiled wort, slightly more rapidly than the unboiled ; and 

Yeast mixture solution, at about three times the rate of the 
flour infusion. 

The soluble extract of flour is thereby shown to be capable of only 
a slow fermentation ; this is due to its containing a comparatively low 
proportion of sugar, and much of that of a kind which requires to be 
inverted before it can be fermented. 

269. Comparison between Flour, and its various con- 
stituents fermented separately. — From the baker's point of view, 
it is of very great importance that he should know which of the several 
constituents of flour it is that affords, during fermentation, the gas by 
which his dough is distended. The following experiments were made 
for the purpose of obtaining definite information on this subject — 
ISTo. 1 requires no further explanation. In No. 2, 34 grams of flour 
were mixed with 6 oz. ( = 170 c.c.) of water, being equivalent to 20 per 
cent, of flour in the water. In No. 3, the flour was agitated several 
times with large quantities of water, and allowed to subside between 
each washing, the supernatant liquid being poured off, and only the 
insoluble residue retained. In this manner, the washed insoluble 
residue is obtained, comparatively free from the other constituents. Of 
these three samples, !STo. 2 represents the whole of the flour, No. 1 the 
soluble, and No. 3 the insoluble portion. No. 4 consisted of 20 per 
•cent, flour infusion, with gelatinised starch added ; the whole being sub- 
jected to a temperature of 30° C. for 12 hours before fermentation : 
this method was adopted in order to determine what diastasic effect was 
produced by the flour infusion on the gelatinised starch, it being assumed 
that whatever starch was converted into sugar would, under the influ- 
ence of the yeast, be decomposed with the evolution of carbon dioxide 
gas. No. 5 was a somewhat similar experiment, made with gluten ; 
some flour was doughed, and then the gluten washed as well as practi- 
cable in a stream of water. In order to get as large a surface as possible, 
this gluten was next rubbed in a mortar with clean sand ; it was in this 
way cut up into a ragged mass. The gluten was mixed with water, and 
kept at 30° C. for 12 hours, in order to permit any degrading action, 
that warm water is capable of exerting on gluten during that time, to 
assert itself. In Nos. 4 and 5, yeast was added at the end of 12 hours. 
No. 6 was a repetition of No. 4, except that the gelatinised starch and 
flour infusion were mixed immediately before fermentation. In No. 7 
the starch was simply added to the flour infusion without previous 
gelatinisatiOn. No. 8 consisted of wheat-starch and water only, to which 
yeast was added. The starch used for these experiments was specially 
prepared in the laboratory from the best Hungarian flour by washing 
the dough, enclosed in muslin, thus separating the gluten. The starch 
was allowed to settle, and the supernatant liquid poured off ; the starch 



148 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

was then stirred up with some more water, and again allowed to sub- 
side. These washings were repeated daily for about a fortnight, at the 
end of which time the starch was air dried. On being tested with 
Fehling's solution the starch gave no trace of precipitate : its purity 
was therefore assured. This series of fermentation tests altogether 
extended over a period of three days. 
Date, 11th May, 1885. 
No. 1. 20 per cent, filtered infusion of flour, 6 oz. at 30° C. com- 
pressed yeast, ^ oz. 
No. 2. 34 grams flour; water, 6 oz. at 30° C.j compressed yeast, J oz. 
No. 3. Washed insoluble residue from 34 grams of flour; water, 6 oz. 
at 30° C. ; compressed yeast, ^ oz. 
Date, 12th May, 1885. 
No. 4. 20 per cent, filtered flour infusion, 6 oz. at 30° C. ; wheat 
starch, 5 grams taken and gelatinised, cooled, then added to 
flour infusion. Mixture placed in bottle and maintained at 
30° C. for 12 hours ; then ^ oz. compressed yeast added and 
fermentation commenced. 
No. 5. Moist thoroughly washed gluten, 5 grams, triturated in mortar 
with sand in order to expose large surface : gluten with 6 oz. 
of water at 30° C. placed in bottle and maintained at 30° C. 
for 12 hours; then \ oz. compressed yeast added and fer- 
mentation commenced. 
Date, 13th May, 1885. 
No. 6. 20 per cent, filtered flour infusion, 6 oz. at 30° C. ; wheat 

starch, 5 grams, gelatinised ; compressed yeast, \ oz. 
No. 7. 20 per cent, filtered flour infusion, 6 oz. at 30° C. ; wheat 
starch, 5 grams, ungelatinised ; compressed yeast, \ oz. 
Date, 11th May, 1885. 
No. 8. Wheat starch, 5 grams, gelatinised, water, 6 oz. at 30° C. ; 
compressed yeast, J oz. 



II 






TECHNICAL RESEARCHES ON FERMENTATION. 



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150 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD 




FIG. 18. 

No. 1, consisting of 20 per cent, flour infusion gave off very little gas y 
the quantity amounting to only 3*3 cubic inches in eight hours; this is very 
much less than that obtained in the previous series of experiments in 
which a 40 per cent, infusion was employed, the latter gave off 8 - 3 cubic 
inches in five hours. No. 2, containing the whole of the flour, gave off 
gas much more copiously, in eight hours there being 19 - 6 cubic inches 
of gas evolved. After the second hour, the evolution fell of!' slowly but 
regularly : this is well shown in the curve in the diagram. The washed 
residue gave off just the same amount of gas as did the filtered infusion, 
in fact at the end of the fifth hour, No. 3 gave the higher reading. It 
will be noticed that the whole of the flour gives off three times as much 
gas as do the filtered infusion and the washed residue together. The 
reason is that, when flour is shaken with water and then filtered, the 
substances which under the action of yeast evolve gas are not all re- 
moved in the filtrate : they are only separated from the insoluble residue 
with great difficulty, and several washings do not so thoroughly remove 
fermentable matter as to leave the residue completely unfermentable. 
That the fermentation in No. 3 is not due to the insoluble residue is 
proved by the result of experiment No. 5 ; for with well washed and 
kneaded gluten, but very little gas is evolved, the total amount in nine 
hours being only 1*5 cubic inches, and this although the gluten for 
twelve hours previous to fermentation was digested with water at 30° C. 
Much of the fermentable matter of flour belongs to what may be called 
the semi-soluble portion, that is, the part of the flour which is retained by 
an ordinary filter paper, but on kneading is readily separated, by the me- 
chanical action, from the gluten.. , In Nos. 4 and 6 the quantities used are 
the same, but the former of the two samples affords evidence of diastasis 
having been occasioned during the twelve hours for which the gela- 
tinised starch was subjected to the action of the flour infusion. No. 6 at 



TECHNICAL RESEARCHES ON FERMENTATION. 151 

first proceeded somewhat the more rapidly, but evolved very little gas 
during the second hour ; during the third hour, however, it recovered 
itself and proceeded regularly, until at the expiration of six hours the 
evolution of gas ceased, with a total of 33*7 inches. The curve shows 
the sudden drop in gas production very clearly. In No. 4 the fermen- 
tation proceeds rapidly and regularly, falling off towards the end, and 
finishing at five hours with 37*5 cubic inches. As a result of the pre- 
vious diastasis, a larger quantity of gas is evolved, but in each instance 
the greater part of the starch remained behind, as if 5 grams of starch 
were completely changed into sugar, and then by fermentation into 
carbon dioxide and alcohol, the yield of gas would roughly be about 85 
cubic inches at 20° C. The diastasic action of the flour infusion will 
have more or less effected the hydrolysis of the starch into dextrin and 
maltose ; the latter will have undergone fermentation, while the former 
is unfermentable. Experiment No. 8 shows that the diastasis of the 
starch is effected by the flour infusion, and not by the yeast, for where 
pure gelatinised starch and yeast alone are employed, exceedingly little 
gas is evolved ; during eight hours, but 1*2 cubic inches only having 
accumulated. This experiment was allowed to proceed overnight, and 
at the end of twenty-one hours, 7*0 cubic inches had been evolved. 
Another reading was taken at the end of the twenty-second hour, and 
showed that 0*8 cubic inches had been evolved during the hour. It 
would seem that the diastasic action of yeast on pure starch increases 
somewhat after some hours, but within a limit of eight hours, which 
covers the time that flour is in most instances subjected to fermentation, 
little or no action has occurred. Yery striking in connection with this 
is the result obtained in experiment No. 7, for when the ungelatinised 
starch was mixed with flour infusion and subjected to fermentation, 
8 "5 cubic inches of gas were obtained in eight hours. The flour infusion 
must under these circumstances have succeeded in hydrolysing some of 
the starch ; for although starch is washed most carefully, there will 
always be a certain number of cells, whose walls are sufficiently thin, to 
permit diastasis to occur ; and as stated in a previous chapter, some 
investigators are of opinion that even unbroken wheat starch cells are 
comparatively readily attacked by hydrolysing agents. (Refer to 
Chapter VII., paragraph 169). Summing up the results obtained in 
these experiments, it is found that — 

Filtered flour infusion supports fermentation slowly. 

The frequently -washed residue of flour supports fermentation 
at about the same rate. 

The entire flour, mixed with water, evolves about six times 
as much gas as either the filtered infusion or the washed resi- 
due from the same weight. 

Kneaded and washed gluten evolves practically no gas. 

Flour infusion and gelatinised starch together evolve gas in 
considerable quantity. 

The quantity of gas is increased when the infusion and the 
gelatinised starch remain together some time before fermenta- 
tion ; which result is due to diastasis by the albuminoids of the 
infusion. 



152 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Ungelatinised starch, under the influence of yeast and flour 
infusion, evolves a moderately large quantity of gas. 

Gelatinised starch alone, undergoes little or no fermentation 
during a period of eight hours, but ferments slowly after stand- 
ing some twenty hours. 

270. Further investigation of Fermentation of Flour 

Infusion. — In order to further determine the source of gas during the 
fermentation of flour infusion, the following experiments were made. — 
A forty per cent, filtered infusion of stone milled flour, from English 
wheat, was prepared by taking 600 grams of flour, and 1500 c.c. of dis- 
tilled water : these were several times shaken together during half-an- 
hour, and then allowed to subside. The upper layer of liquid was next 
poured off and filtered through washed calico : this was subsequently 
again filtered in the ordinary manner through paper until perfectly 
clear. On testing with iodine no colour was produced, thus showing 
the absence of both starch and erthyro-dextrins. The specific gravity 
of the infusion was 1008*5, being somewhat higher than that of 
the forty per cent, infusion used in a previous experiment. A portion 
of the infusion was tested for sugar, before and after inversion, and 
also for albuminoids. Six ounces of the infusion were then fermented 
at 25° C, with a quarter ounce of Encore yeast. The experiment 
was continued for twenty-two hours, at the end of which time fermen- 
tation had entirely ceased. The clear liquid was then decanted off from 
the layer of yeast at the bottom, and tested for sugar and albuminoids 
as was done in the separate portion of the original infusion. To the 
yeast remaining in the bottle, there was at once added a half-ounce of 
sugar and six ounces of water at 25° C, and the testing apparatus set 
up, and the quantity of gas evolved measured. 

The sugar was estimated in the following manner. — A weighed 
quantity of the flour infusion was raised to the boiling point, and main- 
tained at that temperature for about five minutes, in order to coagulate 
albuminoids ; the loss by evaporation was then made up by the addition 
of distilled water, and the solution filtered. 

Quantities taken = 25 c.c. Fehling's solution. 
50 c.c. Water. 
20 c.c. Forty per cent. Flour Infusion. 

Weight of cuprous oxide, Cu 2 0, yielded = 0-1531 grams. Assuming 
this precipitate to be due to maltose, then 

0-1531 x 0-7758 = 0-1187 grams of maltose in 20 c.c. of the flour in- 
fusion = 1 -48 per cent, of maltose in the flour. 

In the next place, 50 c.c. of the flour infusion were taken, 5 c.c. of 
fuming hydrochloric acid added, and the solution inverted by being 
raised to 68° C. The acid was then neutralised by solid sodium carbon- 
ate, and the solution made up to 100 c.c. with water. This produced a 
twenty per cent, inverted solution. 

Quantities taken = 25 c.c. Fehling's Solution. 
50 c.c. Water. 
20 c.c. Twenty per cent, inverted Flour Infusion. 

Weight of cuprous oxide, Cu 2 0, yielded = 0*1860 grams. 

In 20 c.c. of a forty per cent, solution there would be double this 






TECHNICAL RESEARCHES ON FERMENTATION. 153 

quantity = "I860 x 2 = 0*3720 grams. From this must be deducted the 
amount of precipitate due to the maltose present. 

0-3720 — 0*1531 =0*2189 grams of Cu 2 due to a reducing sugar pro- 
duced by inversion. Assuming this sugar to be cane sugar, or at least 
to have the same reducing power, then 

0*2189 x 0-4791 =0*1048 grams of cane sugar in 20 c.c. of the forty 
per cent, infusion = 1*31 per cent, of cane sugar in the flour. 

The total sugar in the flour would thus be 2*79 per cent. 

After fermentation, the upper liquid from the yeast bottle was also 
tested for sugars, after filtration and coagulation of albuminoids as 
before. The uninverted solution gave no precipitate whatever with 
Eehling's solution. A portion was next inverted with acid in the 
manner already described, 20 c.c. of this solution gave a slight trace of 
precipitate with Fehling's solution, which was too little to weigh. So 
far, the practical result may be summed up in the statement that 
filtered aqueous flour infusion contains two or more varieties 
of sugar, these during the act of • fermentation entirely dis- 
appear. 

The infusion was tested for albuminoids, by distillation with alkaline 
permanganate solution, with the following results, calculated to the per- 
centage present in the flour — 

In the infusion before fermentation — 0*76 per cent. 
„ after „ 0*78 ^ _ „ 

Compared with analyses of other flours, these quantities are low • this 
is probably accounted for by a forty per cent, infusion being made, 
whereas a ten per cent, infusion is used in most analyses ; the more 
dilute solution extracts the somewhat viscous albuminoids with greater 
readiness. The only deduction from these determinations is, that the 
amount of albuminoids in a filtered flour infusion is practically 
unchanged by the act of fermentation, there being no disap- 
pearance whatever of these bodies. The small increase observable 
is probably due to albuminous matter being yielded to the solution by 
the yeast itself. 

The following are the results of the fermentation experiments — 

No. 1. Flour Infusion, 6 oz. ; Encore Yeast, \ oz. ; Temperature 
25° C. 

No. 2. Yeast from previous experiment after cessation of fermenta- 
tion : sugar, J oz. ; water, 6 oz., at 25° C. 



154 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 





Gas Evolved in Cubic Inches. 


Time. 








No. i. 


No. 2. 


O ... 


O'O > 

1 I7 
17 1 

^ 33 
67 { 


O'O 






I hour 


5'o 






2 , hours 




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73*5 








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22 „ 





As six ounces of the forty per cent, flour infusion would contain the 
soluble matter of 68 grams of flour, it follows that there would be 
present according to the analysis, 1-89 grams of sugar. This quantity, 
if entirely converted during fermentation into carbon dioxide and alco- 
hol, would yield about 32 cubic inches of gas at 20° C. By the method 
adopted for testing, 1 5 cubic inches were registered at the end of twenty- 
two hours ; to this would have to be added a correction for the amount 
lost by absorption by the water, in order to obtain a correct estimate. 
It is difficult, when the total quantity of gas evolved is small, to deter- 
mine with accuracy the loss by absorption, because the gas in the 
apparatus consists of a mixture in which air is predominant, consequently 
the rate of absorption is less than with pure carbon dioxide gas. If it 
were desired to accurately estimate the quantity of gas, collection over 
mercury would have to be adopted. This is of little importance in the 
present experiment, because the total measured comes well within 
the amount of gas that the sugar would theoretically yield. In other 
words, there is no need to go outside the sugar to find a source from 
which the carbon dioxide is obtained, as the whole of the sugar disap- 
pears, and in the act of fermentation is capable of yielding more gas 
than that observed to be evolved. That the cessation of fermentation 
is not due to the exhaustion of the yeast is proved by experiment No. 2, 
in which the same yeast has more sugar added to it, when a vigorous 
fermentation was immediately set up. That the cessation of fermenta- 
tion is due to the exhaustion of the sugar is proved by that compound 
being absent on analysis of the infusion after fermentation. Summing 
up the whole of the results — 



TECHNICAL RESEARCHES ON FERMENTATION. 



155 



Flour Infusion. 

Before Fermentation. After Fermentation. 



Sugar, 1-89 grams in the six 
ounces of infusion. 

Albuminoids, 0'517 grams pre- 
sent. 



Sugar, absent. 



Albuminoids, 0*530 grams pre- 
sent. 



15 cubic inches of gas 
evolved, 



When Fermentation had ceased, 
had been 
and the yeast was still 
unexhausted, and capable of in- 
ducing fermentation in fresh 
sugar solution. 

Reasoning on these results, together with those obtained in the series 
of experiments on flour and its various constituents taken separately, 
the only logical conclusion is that the fermentation of dough is essentially 
a saccharine fermentation. 

It may be demurred that the circumstances are different in an 
aqueous infusion to those which hold in a tough elastic mass such as 
dough. But it is inconceivable that the fermentation actually imme- 
diately depends on the conversion of any but soluble constituents of the 
flour into gas ; therefore, if those albuminoids, so soluble as to pass 
through filter paper, are not capable of yielding gas as a result of fer- 
mentation by yeast, it follows that the more insoluble albuminous 
compounds likewise will not yield gas. The fact that washed gluten 
yields no gas affords corroborative proof of this point. (The small 
quantity actually obtained by experiment may be accounted for by the 
well-known difficulty of actually freeing gluten from all starchy and 
soluble matters). That the fermentation of the flour itself yields several 
times more gas than does the filtered infusion, lends no support to the 
theory that it is the albuminous matter that is evolving gas, because it 
has been shown that pure ungelatinised starch causes a marked evolu- 
tion of gas, being doubtless first converted into dextrin and maltose by 
diastasis. The fermentability of the washed residue is also accounted 
for by its containing starch. Supposing even that in dough, after 
fermentation had ceased, sugar as such existed and could be removed 
and detected by analytic methods, that of itself would be no proof of 
the evolution of gas being at the expense of the albuminoids, or pep- 
tones derived therefrom (for the argument equally applies to these latter 
bodies), because simultaneously with the fermentation produced by the 
yeast there is a production of sugar by diastasis of the starch. Fermen- 
tation of sugar in a stiff dough is rough work for yeast cells, and it may 
well be that after a few hours they are thoroughly exhausted, and 
disappear through disruption of their cell walls : the continuance of 
diastasis would still cause the slow production of more or less sugar. 
Further, the diastasis of the starch must throughout fermentation pre- 
cede its subsequent conversion into carbon dioxide and alcohol ; and so, 
if the reaction be stopped at any point, more or less sugar would as a 
rule be found. Again drawing a conclusion, the fermentation of 



156 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

dough is in part due to the fermentation of the sugar 
present, in part to the diastasis of a portion of the starch of 
the flour and its subsequent fermentation : these sources are 
sufficient, and more than sufficient, for the production of all the 
gas evolved : these statements admit of experimental proof. 
There is no satisfactory evidence in favour of the gas evolved 
being in any sensible degree derived from the albuminous 
constituents of dough. It should be noticed that no assertion is 
made that no gas whatever is derived from the albuminous constituents 
of flour ; it is possible that in extreme cases, gas is produced from 
albuminous matters as a result of butyric and putrefactive fermenta- 
tions ; but in ordinary breadmaking, as it holds in the United Kingdom, 
the amount of gas derived from this source is of no importance compared 
with that from sugar, and indirectly from starch. Whatever amount 
of gas there is, that is thus obtained from albuminoids, is the result, not 
of the action of yeast, but of bacteria. Further, the statement that 
albuminous bodies do not themselves evolve gas during panary fermen- 
tation must not be construed into meaning that they do not affect the 
quantity evolved. In their capacity as nitrogenous yeast foods, they aid 
the yeast in its development and cousequently in its production of gas 
by decomposition of saccharine bodies. 

271. Effect of Salt on the Fermentation of Flour.— 

Most bakers are familiar with the general statement that salt retards 
fermentation : in order to determine the amount of such retardation 
the following experiments were made. In the first, flour and water 
alone were fermented ; the others consisted of flour mixed with salt 
solutions of various strengths. The appended table contains the results : 
as a matter of convenience in engraving, the curves are shown at the 
right hand side of the diagram, Figure 17, paragraph 268. 
Date, 27th May, 1885. 
No. 1. Flour, 34 grams; water, 6 oz. at 30° C. ; compressed yeast, 

J oz. 
No. 2. Flour, 34 grams ; water, 6 oz. at 30° C. ; compressed yeast, 

^ oz. ; salt, 2*5 grams = 1"4 per cent, salt solution. 
No. 3. Flour, 34 grams ; water, 6 oz. at 30° C. ; compressed yeast, 

\ oz. ; salt, 5'0 grams = 2*9 per cent, salt solution. 

No. 4. Flour, 34 grams ; water, 6 oz. at 30° C. ; compressed yeast, 

\ oz. ; salt, 8*5 grams = 5*0 per cent, salt solution. 



TECHNICAL RESEARCHES ON FERMENTATION. 



157 



Time. 


Gas Evolved in Cubic Inches. 


Temperature. 


No. i. 


No. 2. 


No. 3. 


No. 4 . 


O 

1 hour 

2 hours ... 

3 .. .. 

4 „ 

5 » ••• 

6 „ ... 

7 „ -. 


O'O-, 

•3-oJ 
11-5. 

•3-9 j 

i8-2 = 
19*2 J 


-1*5 

- 2-4 

- 2-6 


o*o. 
} 37 

I2'4 { 
IOO< 

I2 J 2,1 

}i7 

}- o-6 
i5*8 J 


} 3-8 
3-8 { 

} 37 
75=5 

V 2-6 

I0'I< 
I2'2 J 

\ 1-6 

\ i-3 

I5,I l a 

V 06 

i57 j 


O'CK 

I 24 
39 < 

h 2- 9 
6-8^ 

} 2'6 

9'4i 
} 23 

} i-6 

I3-3 < 

h 0-9 

14-2 J 


30.O 

31 -o 

29-5 
29'0 

29-5 
297 
30-0 
29*6 



In the first test, 19 '2 cubic inches of gas were evolved in seven hours, 
while with 1*4 per cent, of salt present in the solution (No. 2) the gas 
was diminished to 15*8 cubic inches. A remarkable occurrence was 
noticed in these two experiments : the reading at the end of the third 
hour was less than that at the end of the second : the evolution of gas 
seems to have entirely stopped for a time, while some of that which had 
been evolved was re-absorbed. It is difficult to account for this diminu- 
tion, especially as it occurred in only two of the tests that were being 
made at the same time. It is not due in any way to leakage, because 
with an apparatus arranged as this is, leakage could only cause an ab- 
normal increase in the volume of the gas. The irregularity having been 
observed, it was thought well to mention it as being a point of some 
interest, and also on the principle that whenever an experiment is 
quoted, the account should be absolutely impartial. The curves in this 
particular diagram are set out in a somewhat different manner to those 
which have preceded : they were so closely identical at several readings 
that if set off from the same zero it would have been extremely difficult 
to distinguish one from the others. Accordingly, the zero of each was 
commenced on a separate line. In this case, the number of each curve 
is given under the zero, and the hours at which the readings were taken 
are marked to the right hand side below the curve. With the exception 
of the break during the third hour of Nos. 1 and 2 the whole of these 
curves are very regular. Between Nos. 2 and 3 there is very little 
difference ; gas was evolved more rapidly from No. 2 at the outset, but 
at the end there was a difference of but 0*1 cubic inch. No. 4 solution, 
containing 5 per cent, of salt, gave off gas more slowly at the first, gain- 
ing a little after, but throughout fell behind the others. Summing up 
the conclusions derived from this series of experiments — 

The use of a 1 -4 per cent, solution of salt, instead of water, 
produced a marked diminution in the evolution of gas. 



158 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Increasing 1 the amount of salt to 2 9 per cent, made very- 
little difference on the speed of fermentation. 

With 5*0 per cent, of salt, gas was evolved still more slowly. 

272. Effect on Fermentation of addition of various 

Substances to Yeast Mixture. — Taking yeast mixture as being 
a substance well fitted to undergo fermentation, the following experi- 
ments were made in order to determine the effect of the addition of 
certain other substances which have an important bearing on the fer- 
menting operations involved in breadmaking. The appended table de- 
scribes sufficiently the substances used in each test of the series ; the 
quantity of yeast mixture was constant throughout. 
Date, 19th May, 1885. 
No. 1. Yeast mixture, \ oz. ; compressed yeast, \ oz. ; water, 6 oz. a 
30° C. 
Date, 12th May, 1885. 
No. 2. Yeast mixture, \ oz. ; compressed yeast, \ oz. ; water, 6 oz. at 

30° C. ; pure wheat starch, 5 grams. 
No. 3. Yeast mixture, \ oz. ; compressed yeast, \ oz. ; water, 6 oz. at 
30° C. ; wheat starch, 5 grams, gelatinised and allowed to 
cool. 
Date, 14th May, 1885. 
No. 4. Yeast mixture, J oz. ; compressed yeast, \ oz. ; water, 6 oz. at 
30° C. ; raw flour, 5 grams. 
Date, 13th May, 1885. 
No. 5. Yeast mixture, J oz. ; compressed yeast, J oz. ; water, 6 oz. at 
30° C. ; flour, 5 grams, gelatinised with small quantity of 
water, and allowed to cool. 
No. 6. Yeast mixture, J oz. ; compressed yeast, \ oz. ; water, 6 oz at 
30° C. ; potato, 5 grams, boiled. 
Date, 18th May, 1885. 
No. 7. Yeast mixture, \ oz. ; compressed yeast, \ oz. ; potato, 5 grams, 
in small pieces, boiled; clear filtered water employed for 
boiling them, made up to 6 oz. at 30° C, and used instead 
of ordinary water. 
No. 8. Yeast mixture, \ oz. ; compressed yeast, \ oz. ; water, 6 oz. at 
30° C. ; salt, 5 grams = 2*9 per cent, salt solution. 
Date, 19th May, 1885, 
No. 9. Yeast mixture, \ oz. ; compressed yeast, \ oz. ; water, 6 oz. at 

30° C. ; salt, 2*5 grams = 1*4 per cent, salt solution. 
No. 10. Yeast mixture, \ oz. ; compressed yeast, \ oz ; water, 6 oz. at 
30° C. ; salt, 8 '5 grams = 5 per cent, salt solution. 



TECHNICAL RESEARCHES ON FERMENTATION. 



159 



Gas Evolved in Cubic Inches. 



Time. 

... 

1 hour 

2 hours 
3 
4 
5 
6 

7 

8 

9 

io 



... 

1 hour 

2 hours 

3 »• 

4 <> 

5 » 

6 „ 

7 >, 

8 ., 



No. i. 




74*5 



No. 6. 



O'O 




No. 2. 




No. 7. 



o-o 



22*0 




No. 3. 



I 5 '2. 

45 "<>' 

90'5' 



"9'5 



15-2 
292 

45'5 
29-0 



J28-I 

147-6 ] 

^20*2 
l6 7 -8 ] 

Yio'o 
177-8] 

Y 50 

182-8] 

[ 0*2 
l8 3 -o] 

183-5 J 



No. 8. 




No. 4. 



i»4 



18-4] 

h39 J 
57-5 

h42*5 
ioo-o< 

J 32 ' 6 

132-6] 
164-3 i 

I 9-2 

173-5] 

} 17 



75*2 



No. 9. 




178-0 



No. 5. 



O'O 




209-4 



No. 10. 



o-o 




160 



CHEMISTRY OF WHEAT, FLOUE, AND BREAD. 



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Fig. 



In the accompanying diagram. Fig. 19, the curves representing the 
above results are set out. As in many instances they resemble each 
other very closely, each curve is drawn from a separate zero, underneath 
which is placed the number of the experiment. The numbers underneath 
and to the right of the curves indicate the hours at which the respective 
readings were taken. No. 1 simply represents the evolution of gas by 
the yeast mixture and water only, when fermented : the action was very 
regular, and ceased entirely at the end of six hours. No. 2 is the same 
mixture, together with the ungelatinised wheat-starch, from the same 
sample as was described as used in certain previous experiments. The 
results of ISTo. 2 are identical with those of No. 1, showing that the 
starch under these circumstances is unacted on. This experiment stands 
out in contrast to that in a previous series (paragraph 269) in which 
ungelatinised starch was added to flour infusion. There, a diastasic 
agent was present, and diastasis of the starch ensued ; here with yeast 
only the starch remains throughout unaltered. In No. 3 the starch 
was gelatinised and allowed to cool ; in this case there is for the first 
five hours a marked diminution in the evolution of gas : this is most 
likely due to the viscous nature of the liquid containing starch in solution^ 
the effect being a mechanical one, resulting from a physical retardation 
of fermentation. During the latter part of the experiment the pro- 
duction of gas exceeds that in No. 1, amounting to 183*5 against 174.5 
cubic inches, and does not terminate until the end of ten hours, whereas 
both Nos. 1 and 2 ceased within six hours. In No. 4 raw flour is 
substituted for ungelatinised starch : again, a series of readings are 
obtained, closely resembling Nos. 1 and 2, and showing that with yeast 



TECHNICAL RESEARCHES OX FERMENTATION. 161 

mixture as a basis, raw flour produces no appreciable action. But when 
the flour is gelatinised as in No. 5, the evolution of gas is more copious 
and more rapid : the curve more nearly approaches the vertical, and at 
the end of eight hours a total of 209*4 cubic inches of gas is registered, 
with an increase during the last hour of 1*2 cubic inches. Gelatinised 
flour favours fermentation to a much greater extent than does gela- 
tinised starch ; the principal chemical difference between the two is that 
in the former there are present the albuminoids of the flour non-coagulable 
by heat. To No. 6 were added 5 grams of potato, boiled : the result is 
a considerable increase in the amount of gas evolved, which shows itself 
more particularly during the earlier period of fermentation : boiled 
potato therefore acts as a stimulant, and also furnishes saccharine matter 
as food for the yeast. Experiment No. 7 was suggested to the author 
by the gentleman whose papers on Breadmaking in the " British and 
Foreign Confectioner" above the nom de plume of "Tablier Blanc " are 
so well known to the readers of that Journal. It is remarkable, and 
contrary to the generally received ideas, to find that the clear filtered 
water in which potatoes were simply boiled, exercises such marked in- 
fluence on fermentation. The increase in rapidity of production of gas 
is very nearly as great as when the whole of the potatoes are used. In 
No. 7, 9 more cubic inches of gas are evolved than in No. 1, the action 
terminating at the same time. It may be of interest to mention here, 
that in some parts of Lancashire, where it is a prevalent custom for 
families to make their own bread, they adopt the plan of setting the 
sponge with water in which the potatoes have been boiled. The bread 
produced is among the best with which the author is acquainted. Nos. 
8, 9, and 10, were similar experiments to those of the preceding series 
(paragraph 271), except that the action of salt was tested on yeast 
mixture instead of on flour. No. 8 shows a slightly less quantity of 
gas evolved than does No. 1. No. 9, on the other hand, shows a decided 
increase in the quantity of gas over that evolved either in Nos. 1 or 8. 
In No. 10, however, where 5 per cent, of salt is employed, the gas falls 
off to 165*2 cubic inches in seven hours, although at the end of the time 
fermentation is still actively proceeding. Summarising the results of 
these experiments, 

The addition to yeast mixture of — 

Ungelatmised wheat-starch has no practical effect on fer- 
mentation. 

Gelatinised wheat-starch at first retards the action, 
which afterward is slightly accelerated. 

Raw flour produces very little action. 

Gelatinised flour induces a much more rapid and 
copious evolution of gas. 

Boiled potato produces a similar effect to gelatinised 
flour, but to a less extent. 

The water used for boiling potatoes is almost as effective 
as the potatoes themselves. 

Quantities of salt, up to 3 per cent, of water used, do 
not retard fermentation greatly : above that quan- 
tity salt considerably diminishes the evolution of gas. 



162 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



273. Effect on the Fermentation of Sugar of the addition 

Of Flour and Potatoes. — As yeast mixture contains within itself, 
not only sugar but also other ingredients which stimulate a rapid fer- 
mentation, it was thought advisable to repeat some of the preceding 
experiments with sugar only. Accordingly, the experiments recorded 
in the following table were performed. The corresponding curves are 
shown in the diagram, Fig. 20. The curve marked 1A, is copied from 
the diagram illustrating the effect of variations of temperature, Fig. 21, 
and represents the gas evolved during the fermentation of ^ ounce of 
sugar, and six ounces of water at 30° C, with a J ounce of yeast. It is 
here introduced for the sake of comparison. 

Date, 21st May, 1885. 

No. 1. Sugar, J oz. ; compressed yeast, J oz. ; water, 6 oz. at 30° C. ; 
raw flour, 5 grams. 

No. 2. Sugar, J oz. ; compressed yeast, \ oz. ; water, 6 oz. at 30° C. ; 
flour, 5 grams, gelatinised in small quantity of water and 
allowed to cool. 
Date, 18th May, 1885. 

No. 3. Sugar, \ oz. ; compressed yeast, \ oz. ; water, 6 oz. at 30° C. ; 
potato, 5 grams, boiled. 

No. 4. Sugar, \ oz. ; compressed yeast, J oz. ; potato, 5 grams, in 
small pieces, boiled ; clear filtered water employed for boil- 
ing them, made up to 6 oz. at 30° C, and used instead of 
ordinary water. 



Time. 


Gas Evolved in Cubic Inches. 


No. i. 


No. 2. 


No. 3. 


No. 4. 




1 hour 

2 hours 

3 " 

4 „ 

5 >, 

6 „ 

7 „ 

8 „ 

9 „ 

10 ,, 


0*0 , 

i9-o 
i 9 -o 

19-2 
38'2 

15-7 
53'9 

i8- 3 
62-2 

io-8 
73-o 

84-3 

14-1 

98-4 

n-9 
no'3 

9'o 
119-3 ; 


O'Oj 

13-2 

21-9 

35'i 

26-9 
608 

Y 20-2 

81 -o 

29-0 

IIO'O 

25-0 

i35-o 

22.3 
I57-3 

15-2 

172-5 

[ IO'I 

182-6 > 


o-o , 

15-0 
15-0] 

J- 26-2 

41 '2 \ 

^ f 25 ' 3 

66 -5 { 

I 23-5 
90-0^ 

A 27 ' 6 

117-6* 

I 20-5 
138-1 

\ 17-0 
i55*M 

< J I3 ' 9 
169-2 < 

r I2,3 
181-5] 

I 4-3 

186-8 J 


o-o. 

y io-o 
wo*. 

[23-8 

33-8^ 

} 24-3 

84*0] 

I 30*4 
H4'4< 

I 19-2 
133-6^ 

\ 17*2 
150-8 { 

I 14-2 
165-0^ 

jio-i 

\ 8-4 
183-5 j 



TECHNICAL RESEARCHES ON FERMENTATION. 



163 




FIG. 20. 

In the first experiment, with raw flour, the quantity of gas evolved 
keeps very close to that evolved from the sugar solution and yeast only, 
until three hours have elapsed. After that time the speed of evolution 
of gas falls off sharply, until in nine hours the quantity of gas evolved 
is only just as much as the sugar alone had evolved in six hours. The 
actual diminution of speed of the evolution of gas, as a result of the 
presence of flour, is noticeable in several experiments. With gelatinised 
flour, on the other hand, the fermentation proceeds more rapidly, and 
to a greater extent than with sugar only, as in 1 A. The speed of pro- 
duction of gas is less than in the corresponding experiment of the 
previous series with yeast mixture,' but as the action continues longer 
before commencing to fall off, the actual amount of gas evolved is about 
the same. The result of No. 3. with boiled potato is almost similar to No. 
2. No. 4., containing boiled potato water, ferments at almost exactly the 
same rate as did No. 2. with the whole of the potato. Summing up, 
The addition to sugar of — 

Raw flour retarded the fermentation in the latter part of 

the experiment. 
Gelatinised Flour, boiled potato, and boiled potato water, 
each stimulated and increased the amount of fer- 
mentation to about the same degree. 
274. Effect of Temperature on Fermentation. — In order to 

measure quantitatively the effect of variations of temperature on the 
production of gas by fermentation, the following series of experiments 
were made : — Two different brands of compressed yeast were employed, 
one of which is designated yeast, "A," the other yeast, " B ; " the same 
quantity of yeast was employed throughout the experiment. The series 
included tests by each yeast on sugar, yeast mixture, and flour, at the 
respective temperatures of 20°, 25°, 30°, and 35° C. = (68°, 77°, 86°, 



164 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



and 95° F.) In the following tables each series of tests is distinguished 
by a letter in order to admit of more easy reference. 

Date, 3rd July, 1885. — The complete series at 20° C. made this day. 
„ 2nd July, 1885.— „ „ 25° C. 

„ 30th June, 1885.— „ „ 30° C. 

„ 29th June, 1885.— „ „ 35° C. 

No. 1. Yeast mixture, J oz. ; compressed yeast, A, \ oz. ; water,. 

6 oz. at 30° C. 
No. 2. Yeast mixture, \ oz. ; compressed yeast, A, \ oz. ; water,. 

6 oz. at 25° C. 
No. 3. Yeast mixture, \ oz. ; compressed yeast, A, \ oz. -, water,, 

6 oz. at 30° C. 
No. 4. Yeast mixture, J oz. ; compressed yeast, A, J oz. ; water,, 
6 oz. at 35° C. 



A 


Gas Evolved in Cubic Inches. 


Time. 


No. i at 2o° C. 


No. 2 at 25 ° C. 


No. 3 at 30 ° C. 


No. 4 at 35 ° C. 




1 hour 

2 hours 

3 „ 

4 „ 

5 ,, 

6 „ 


O'O. 

> 20 
2'0< 

J 3 5^ 

o f I4 " 5 

28-0^ 

\i6-7 
447 < 

[ 20'3 

\ i8'8 
8 3 -8 J 


O'O . 

y 100 

I0'O< 

}i 9 '8 
29-8^ 

V23'2 

53*o< 

V 22 
75 -o{ 

\ 19*0 
94'o < 

} i9'3 
113-3 J 


O'O -v 

[287 
287 { 

} 3i '9 
60 '6 < 

}436 
104-2 J 

\ 40-8 
i45-o 1 

} 30'o 
i75-o< 

\ 2-8 
177-8 J 


00. 

} 3 8'o 

84-1 { 

h 43*9 

128-0^ 

} 3i'9 
159*9^ 

)i 5 -i 

V o-o 
i75'o J 



No. 1. Sugar, J oz. ; compressed yeast, A, J oz. ; water, 

t» J No. 2. Sugar, \ oz. ; compressed yeast, A, J oz. ; water, 

v No. 3. Sugar, \ oz. ; compressed yeast, A, \ oz. ; water, 

No. 4. Sugar, \ oz. ; compressed yeast, A, \ oz. • water, 



6 oz. at 20° C. 
6 oz. at 25° C. 
6 oz. at 30° C. 
6 oz. at 35° C. 



B 


Gas Evolved in Cubic Inches. 


Time. 


No. 1 at 20 ° C. 


No. 2 at 25 ° C. 


No. 3 at 30 ° C. 


No. 4 at 35 C. 




1 hour 

2 hours 

3 >, 

4 „ 

5 » 

6 „ 


O'O^ 

1 3 ^ 

} 67 

} 6-5 

13-5 < 

I 7 ' 4 
20-9 \ 

} 8 ' J 
29-0^ 

\ 7'5 
36-5 j 


O'O -, 

\ 7-0 
7-o< 

J- I2'0 
'9-0 { 

\ I3-0 

f i3-o 
45 'o< 

h 13*0 
58-1 

h i4'i 

72*2 J 


0'0-> 

\ I5'0 

15-0 

| 17-5 
32-5 { 

\ 22-6 

55-i 

V 20-9 

75 -o< 

}• 29-0 
104*0 < 

h i4'o 
U8-0-' 


O'O-v 

I 20-5 
20-5 < 

[24-5 

45 'o< 

\ 25*0 
70-0^ 

\ 23 
93 'o< 

^ 23.2 

II6-2 < 

L 18-6 
134-8 J 



TECHNICAL RESEARCHES ON FERMENTATION. 



165 



C No. 1. Flour, 34 grams; compressed yeast, A, \ oz. ; water, 6 oz. 

at 20° C. 
I No. 2. Flour, 34 grams ; compressed yeast, A, \ oz. ; water, 6 oz. 
c I at 25° C. 

' No. 3. Flour, 34 grams ; compressed yeast, A, \ oz. ; water, 6 oz. 
at 30° C. 
No. 4. Flour, 34 grams • compressed yeast, A, \ oz. ■ water, 6 oz. 
at 35° C. 



Time. 



O 

1 hour 

2 hours 

3 » 

4 „ 

5 » 

6 ,. 



Gas Evolved in Cubic Inches. 



No. i at 2o° C No. 2 at 25 ° C. 




O'O 



3*o 



} 3*o 
I 37 

I2'2 I 

} 2-5 

147 < 

Y 2-0 

167 { 

I8-2- 1 



No. 3 at 30 ° C. 



O'O 




244 



No. 4 at 35 ° C. 






[No. 1. 


Yeast mixture, \ 


oz. ; compressed yeast, B, 


J oz. ; water, 






6 oz. at 20° C. 






No. 2. 


Yeast mixture, J oz. ; compressed yeast, B, 


J oz. ; water, 


D- 




6 oz. at 25° C. 




No. 3. 


Yeast mixture, \ oz. ; compressed yeast, B, 


J oz. ; water, 






6 oz. at 30° C. 






No. 4. 


Yeast mixture, \ oz. ; compressed yeast, B, 


J oz. ; water, 






6 oz. at 30° C. 




D 


Gas Evolved in Cubic Inches. 


i 


Time. 


No. 1 at 20 ° C. 


No. 2at25°C. 


No. 3 at 30 °C. 


No. 4 at 35 ° C. 

o-o ^ 

\ 517 

\ 51*3 
103-0^ 

U8-7 

I 27*5 
179-2 { 

Y o-8 
180-0^ 

V o-o 
180-0^ 


O 




O'O-v 


O'O^ 


oo-> 

\ 2*45 
24'5 i 

\ 39*o 
63-5 { 

\ 47*2 
1107^ 

[36-8 

147*5 i 

Y 29-0 
176-5 

} 2-8 
1794 J 








\ 5-6 


\ II'O 


I hour 




5-6 \ 


u-o 








177 


[26-3 


2 hours 




23'3 \ 




37*3 \ 

\ 27"9 
65-2 

U6-3 
9i'5{ 

Y 22-0 

\ 18-9 
132*4 J 








- 19-0 


3 » 




42*3^ 










18-9 


4 „ 




6l'2<j 










- 19-8 


5 » 




8i-o<{ 

\ 19*4 
100-4-' 


6 „ 





166 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



No. 1. Sugar, \ oz.; compressed yeast, B, \ oz. ; water, 6 oz. at 20° C. 

-p, J No. 2. Sugar, J oz. ; compressed yeast, B, J oz. ; water, 6 oz. at 25° C. 

u i No. 3. Sugar, J oz. ; compressed yeast, B, | oz. ; water, 6 oz. at 30° C. 

No. 4. Sugar, J oz. ; compressed yeast, B, | oz. ; water, 6 oz. at 35° C. 



E 


Gas Evolved in Cubic Inches. 


Time. 


No. i at 20 ° C. 


No. 2 at 25° C. 


No. 3 at 30 ° C. 


No. 4at 3 5°C. 


o 

i hour 

2 hours 

3 » 

4 >, 

5 » 

6 „ 


O'O . 

7*3 
7-3 \ 
} H7 

y i2-2 

}n-8 

43*0 i 

} 12-5 

6 7 J lr5 


O'O. 

77 { 

} 7-3 
25'° i 

}i87 
437 \ 

6,2} I7 ' 5 
t 17-8 
79'o { 

98-0 * 


\ 7*2 

V 24-9 

42-1 .< 

\ 297 

\ 257 
97*5 < 

f 32-0 

I 6-o 


V 27-0 ; 
27-0^ 

\3i'6 

I 26-4 
85-0] 

\ 30-0 

y 26*0 
i 4 ro{ 

f 2T0 
162*0 > 



FJ 



No. 1. Flour, 34 grams; compressed yeast, B, \ oz. ; water, 6 oz. 

at 20° C. 
No. 2. Flour, 34 grams ; compressed yeast, B, \ oz. ; water, 6 oz, 

at 25° C. 
No. 3. Flour, 34 grams ; compressed yeast, B, \ oz. ; water, 6 oz. 

at 30° C. 
No. 4. Flour, 34 grams; compressed yeast, B, \ oz. ; water, 6 oz. 

at 30° C. 



F 


Gas Evolved in Cubic Inches. 


Time. 


No. 1 at 20 ° C. 


No. 2 at 25 ° C. 


No. 3 at 30 ° C. No. 4 at 35 C. 




1 hour 

2 hours 

3 » 

4 „ 

5 » 

6 „ 


O'O-, 

i-6{ 

\ 2-4 
4-o \ 

y 2*2 

87 

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\ i-6 

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3'8 

5-9 
9-7] 

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24*3 J 


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II'O^ 

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I 4-6 

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I 27 
247 < 

\ 3*1 

27-8] 

J I>4 
29-2-' 


0*0 ■» 

[12-3 
} 6 ' 7 

} 3*2 
22*2 < 

[ 3'3 

25-5 < 
\ 27 

28 '2 { 

} I? 
29*9 } 



TECHNICAL RESEARCHES ON FERMENTATION. 



167 



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FIG. 21. 

Figure 21 gives the curves of the series A, B, D, E, in the order of 
their sequence. The two Flour series, C and F, are given separately in 
Figure 22, because of their being drawn to a different vertical scale. 
Considering first the A series, consisting of yeast A with yeast mixture, 
a temperature of 25° C. increases the total quantity of gas considerably 
over that evolved at 20° G; a further increase to 30° more than doubles 
the average speed of evolution of gas. Beyond 30° the amount of gas 
evolved is not materially increased with the rise in temperature, thus 
at 35° C. there is very little more gas evolved than at 30° C. In the B 
series, where the sugar is substituted for yeast mixture, the production 
of gas is less, but the same general relation exists between the various 
members of the series. 



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FIG. 22. 



168 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

With flour, on the other hand, there is a more equal increase between 
each member of the series, but still there is a greater increase between 
Nos. 2 and 3 than the others. The remaining series of tests, D, E, F, 
are an exact repetition of A, B, and C, except in the employment of a 
different brand of yeast. Again, very much the same distinctions are 
observable between the members of the same series ; this is readily seen 
by an examination of the sets of curves in D and E. It should be 
pointed out that the yeast B gives off, in every case, more gas during 
the same time than did yeast A in the corresponding experiment. 
This difference is not so striking in the two sets A and D, because, with 
the stimulating effect of the yeast mixture, the weaker yeast is helped 
proportionately the more. But in sugar, each yeast has to depend 
more fully on its own vitality in producing fermentation. Consequently, 
the stronger yeast B causes the evolution of a proportionately higher 
quantity of gas than does the yeast A. The result is that there is not 
so much difference between the sets of curves D and E as there is 
between the curves A and B. The second yeast caused, in the Flour 
series F, at the higher temperatures a more rapid evolution of gas than 
did the first. The curves for 30° and 35° C. are almost identical. For 
the first four hours the yeast B caused a remarkably rapid evolution of 
gas : at the end of that time the experiment was spoiled through an 
accident to the apparatus. At 20° C, yeast B gave off somewhat less 
gas from the flour mixture than did yeast A : out of the 24 different 
tests this is the only one in which the second yeast produced less gas. 
Summarising the results obtained — 

In the three media employed, the rapidity of production of 
gas increases with the temperature ; this increase is more 
marked between 25° and 30° than between 30° and 35° C. 

275. Results of using different quantities of Yeast. — 

In the first series of experiments described (paragraph 267) two com- 
plete sets were made, the one with an eighth of an ounce of yeast, the 
other with a quarter of an ounce. As might be expected, with the 
greater quantity, more gas was evolved during the same time, but the 
effect of using twice as much yeast was not to cause twice as rapid an 
evolution of gas. The following experiments had as their object the 
study of the effect of varying the quantity of yeast, on the amount of 
gas evolved. The yeasts A and B, are the same as have been already 
referred to under those names. 
Date, 14th July, 1885. 
No. 1. Sugar, | oz. ; water, 6 oz. at 25° C. ; compressed yeast, ' A,' 

^ oz. = 2 drams. 
No. 2. Sugar, J oz. ; water, 6 oz. at 25° C. ; compressed yeast, ' A,'y\ 

oz. = 3 drams. 
No. 3. Sugar, J oz. ; water, 6 oz. at 25° C. ; compressed yeast, 'A,' 
^ oz. = 4 drams. 
Date, 8th July, 1885. 
No. 4. Yeast mixture, J oz. ; water, 6 oz. at 25° C. ; compressed yeast, 

< A,' i oz. 
No. 5. Yeast mixture, \ oz. ; water, 6 oz. at 25° C. ; compressed yeast, 

< a; t \ oz. 



TECHNICAL RESEARCHES ON FERMENTATION. 169 

No. 6. Yeast mixture, J oz. ; water, 6 oz. at 25° C. ; compressed yeast, 

<A,4oz. 
No. 7. Sugar, \ oz. ; water, 6 oz. at 25° C. ; compressed yeast, 'B,' 

£oz. 
No. 8. Sugar, \ oz. ; water, 6 oz. at 25° C. ; compressed yeast, ' B/ 

No. 9. Sugar, \ oz. ; water, 6 oz. at 25° C. ; compressed yeast, ' B,' 

\ oz/ 
Date, 14th July, 1885. 
No. 10. Yeast mixture, \ oz. ; water, 6 oz. at 25° C; compressed 

yeast, ' B,' \ oz. 
No. 11. Yeast mixture, \ oz. ; water, 6 oz. at 25° C. ; compressed 

yeast, ' B,' -^ oz. 
No. 12. Yeast mixture, \ oz. ; water, 6 oz. at 25° C. ; compressed 

yeast, ' B,' \ oz. 
Date, 15th July, 1885. 
No. 13. Sugar, \ oz. ; water, 6 oz. at 25° C. ; compressed yeast, 'B,' 

\ oz. = 7"1 grams. 
No. 14. Sugar, \ oz. ; water, 6 oz. at 25° C. ; compressed yeast, 'B ' 

6*4 grams = 10 per cent, less than in No. 13. 



170 



CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 



Time. 



O 

1 hour... 

2 hours 

3 » - 

4 „ .- 

5 » - 

6 „ ... 



o 

1 hour... 

2 hours 

3 r, .- 

4 ,, - 

5 » - 



Gas Evolved in Cubic Inches. 



No. i. 



O'O, 

}« 

I2-0^ 

[ 67 
} 67 
I 7-6 



25*4 
33 



37-6 ( 
4*5' 



No. 7. 



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I4"3 i 

28-5 
38-9 J 



No. 2. 



[■ 2'0 

} 7-o 

\ 9'2 

} 9-6 



2 

9-0 
18-2 



9-8 



10*9 



No. 8. 



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2' 4 

14 
26-0 



37' 7 < 

•8{ 
M4*9 

637 J 



No. 3. 




No. 9. 




No. 4. 



No. 5. 



No. 6. 




No. 10. 



0-9 

11*2 



} 0-9 
Mo-3 

}i8-4 
}i4'3 



59*0 
73'3 




o } 8 ' 5 

Uo-8 
29*3 { 

p37 
53'oi 

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79-oJ 

f 22*5 
lOI's{ 

1 39' J 
141*0^ 



No. 11. 



No. 12. 




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[ 6-o 



6-o 



36-2 
64-2 



30-2 
28*0 



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o 

1 hour... 

2 hours 

3 ,. •- 
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No. 13. 



No. 14. 



Ratios be- 
tween 13 & 14 



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5 



437 \ 
h23' 

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} 8-2 
93" 2 J 



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707 { 

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78-0 J 



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rig 

1-06 

1*12 



TECHNICAL RESEARCHES ON FERMENTATION. 



171 



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The first twelve of these results are illustrated in figure 23, those 
obtained with yeast A being first given, and then those obtained by the 
use of yeast B. It may be noticed that the stronger of the two yeasts 
causes throughout the more copious evolution of gas. Unfortunately, 
No. 1 2 test was accidentally spoiled at the end of three hours. In order 
to facilitate a comparison of these tests with each other, the mean, in 
each case, between the eighth and quarter of an ounce tests, has been 
calculated for the total of gas at three and six hours respectively. In 
addition, the means between the quantities of gas evolved in the same 
tests during the fourth hour has been similarly calculated ; these quan- 
tities are those indicated by the numbers placed outside the brackets, 
between the three and four hour readings. The mean of any two 
numbers is obtained by adding them together, and dividing the sum 
by 2. As 3 is the mean between 2 and 4, theoretically one would ex- 
pect that three drams of yeast would cause an evolution of gas closely 
corresponding with the mean of the quantities yielded by 2 and 4 drams 
of yeast respectively. The table below gives these calculated means, 
side by side with the actual quantities obtained by experiment. — 

Means between 2 and 4 dram 
experiments. 

Nos. 1 & 3 at 3 hours, 

„ at 6 hours, 

„ during 4th hour, 

Nos. 4 & 6 at 3 hours, 

„ at 6 hours, - 1 

„ during 4th hour, 

Nos. 7 & 9 at 3 hours, 

,, at 6 hours, 

,, during 4th hour, 

Nos. 10 & 12 at 3 hours, 

,, during 3rd hour, 

An examination of these 
evolved is fairly proportional 



Actual quantities evolved in 3 dram 
experiments. 

18-2 No. 2 at 3 hours, - - 18-2 

47-7 „ at 6 hours, - - 48-5 

9-2 „ during 4th hour, - 9'6 

42-5 No. 5 at 3 hours, - - 42'0 

13-4 „ at 6 hours, - - 105'0 

21-8 „ during 4th hour, - 21 '0 

27-9 No. 8 at 3 hours, - - 26-0 

66*2 „ at 6 hours, - - 63*7 

12-3 „ during 4th hour, - 11 -7 

45-3 No. 11 at 3 hours, - - 48-0 

21-6 „ during 3rd hour, 26'5 
results shows that the quantity of gas 
to the amount of yeast employed ; as the 



172 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

" means " in almost every case agree closely with the gas actually 
evolved in the direct experiments with intermediate quantities of yeast. 
Experiments Nos. 13 and 14 were made in order to determine the effect 
produced by a slight diminution of the quantity of yeast ; in the former, 
half an ounce, 7*1 grams, was taken, while in No. 14, 6*4 grams were 
used, this quantity being ninety per cent, of 7'1 grams. In No. 13, 
93*2 cubic inches of gas were evolved in six hours ; ninety per cent, of 
this amounts to 83*9 cubic inches; whereas in No. 14, with ninety per 
cent, of yeast, but 78*8 cubic inches of gas are produced. Another 
point of interest may be noticed in experiments 13 and 14 ; the rate of 
evolution of gas during each successive hour rises and falls in almost 
exactly the same proportion. Through an oversight, an hour and a half 
was allowed to elapse between the third and fourth reading, but as this 
occurred with the both, the results are still comparative. In each case 
the maximum evolution of gas was during this period of one and a half 
hours. The constancy of this proportion or ratio is best shown by 
dividing one of the numbers by the other : if the ratio between them 
were in every case alike, the resulting quotients would be throughout 
identical. In the table, the column headed " Ratios " consists of figures 
opposite the brackets in No. 13, divided by those in No. 14 ; the last 
four such ratios agree very nearly, thus showing clearly how closely the 
proportional rate of evolution agrees in each case. At the end, when 
the speed of production of gas has fallen off to less than one half during 
the hour, the ratio remains practically the same. Now, in No. 14, the 
quantity of sugar still remaining in the solution must be more than in 
No. 13, and if the rate of evolution fell off only because of there being less 
sugar, a greater falling off might be expected in No. 13 than in No. 14 : 
while as a matter of fact just the opposite occurs, the proportionate 
falling off being slightly more in the latter. Besides the diminution of 
the sugar, another factor is at work in lessening the evolution of gas, 
and that is the gradual exhaustion of the yeast cell : consequently, fer- 
mentation in sugar is particularly valuable where the object is to 
measure the strength or vital capacity for producing fermentation that 
any yeast possesses, especially when the fermentation has to depend on 
the original cells and not on the progeny produced by budding. For 
these reasons, sugar fermentation is, in the author's view, preferable, 
when testing a yeast as to its fitness for bakers' use. Summing up the 
results of these experiments — 

Working at 25° C, with the yeast apparatus, the quantity of 
gas evolved is fairly proportional to that of yeast employed. 

When measuring the strength of yeast for bakers, sugar is 
indicated as the most suitable fermenting medium. 

276. Further comparisons of Fermentation in Flour 

and Sugar Solutions. — Since the greater part of this chapter was 
written, and almost immediately before going to press, some experiments 
were made, which seem to be of sufficient importance to warrant their 
special introduction here. Some samples of French compressed yeast, 
and also of English brewer's yeast, washed and compressed for conti- 
nental export, were forwarded to the author for examination. With 
these yeasts the following series of tests were made — 



TECHNICAL RESEARCHES ON FERMENTATION. 173 



Date, 22nd October, 1885. 

No. 1. Yeast mixture, J oz. ; water, 6 oz. at 25° C. ; French com- 
pressed yeast, \ oz. 

No. 2. Sugar, J oz. • water, 6 oz. at 25° C; French compressed yeast,, 
I oz. 

No. 3. Flour, 68 grams ; water, 6 oz. at 25° C. ; French compressed 
yeast, J oz. 

No. 4. Yeast mixture, \ oz. ; water, 6 oz. at 25° C; compressed Eng- 
lish brewers' yeast, \ oz. 

No. 5. Sugar, J oz. ; water, 6 oz. at 25° C. ; compressed English 
brewers' yeast, \ oz. 

No. 6. Flour, 68 grams ; water, 6 oz. at 25° C. ; compressed English 
brewers' yeast, \ oz. 
Date, 23rd October, 1885. 

No. 7. Sugar, \ oz. ; water, 6 oz. at 25° C. ; compressed English 
brewers' yeast, \ oz. 

No. 8. Flour, 68 grams ; water, 6 oz. at 25° C. ; compressed English 
brewers' yeast, \ oz. 

No. 9. Flour, 68 grams; sugar, £ oz. ; water, 6 oz. at 25° C. ; com- 
pressed English brewers' yeast, J oz. 

No. 10. Sugar, J oz.; water, 6 oz. at 25° C; Brighton brewers' yeast,, 
as skimmed, \ oz, 

No. 11. Flour, 68 grams; water, 6 oz. at 25° C. ; Brighton brewers 
yeast, j oz. 



174 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 





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Nos. 1 and 2 call for no special remark, being similar in character to 
many tests previously made. The quantity of flour in No. 3 is double 
that used in previous experiments, the object being to get a mixture 
which should be a nearer assimilation to dough, while still possessing 
sufficient fluidity to permit the escape of the produced gas. As might 
be expected, the amount of gas evolved is higher than in tests where 34 
grams were used. Nos. 4 and 5 were tests with the compressed brewers' 
yeast — there is a more rapid evolution of gas than in the corresponding 
tests with the French yeast ; so far, the verdict would be in favour of 
the English yeast as being a stronger yeast. This verdict is borne out 
by the results of commercial use of the yeast for brewing purposes. In 
Belgium, the fiscal laws require that distillers shall absolutely complete 



TECHNICAL RESEARCHES ON FERMENTATION. 175 

the fermentation of their wort or " mash " within twenty-four hours ; 
they therefore use the strongest and most energetic yeast obtainable. 
English brewers' yeast is consequently largely exported to Belgium for 
distillers' use, having a preference given it over French and other con- 
tinental yeasts. Next comes test No. 6, the results of which are most 
remarkable ; the English yeast, which had been by far the stronger in 
both yeast mixture and sugar solutions, causes practically no evolution 
of gas whatever from the flour mixture. On the next day some of the 
experiments were repeated, together with others. No. 7 was a duplicate 
of No. 5 (with sugar) and yields similar results ; No. 8 was a duplicate 
of No. 6, and of the two, results in the production of still less gas ; there- 
fore, the results of the first day's experiments were confirmed by those of 
the second. In No. 9, there was added, in addition to flour, a half 
ounce of sugar, with the surprising result that in this case also only one 
oubic inch of gas was evolved in six hours. No. 10, in which a local 
brewers' yeast was used, showed an evolution of gas in large quantity; 
but in No. 11, the same yeast caused an evolution of but one cubic inch 
of gas in six hours. So far as a conclusion can be drawn from these 
few experiments, brewers' yeasts may cause copious evolution of gas 
from yeast mixture and sugar solution, but are unable to produce gas, 
under this system of testing, from dilute mixtures of flour and water. 
Further, little or no fermentation occurs even when sugar is added to 
the flour and water mixture. Under the microscope, both brewers' 
yeasts were healthy in appearance ; the cell walls in the compressed 
sample appeared somewhat thin, but there was no striking divergence 
from the normal. These results obtained on brewers' yeasts are so 
-anomalous, that it was thought due to the readers of this work to insert 
them. At the earliest possible moment, the author will proceed to ex- 
amine these remarkable results more exhaustively, and hopes shortly to 
be able to make public the results of such investigation. It should be 
mentioned that in comparison of yeasts of the same type with each 
other, as for instance the various brands of French compressed yeasts, 
the results of fermentations in flour practically agree with those of 
fermentation in yeast mixture and sugar solutions. 

Experimental Work. 

277- The student who has the opportunity will do well to perform 
for himself most of the experiments described in this chapter, and com- 
pare the results he obtains with those here recorded. He should also 
prepare diagrams of curves representing graphically the quantities of 
gas he finds to be evolved. For this latter purpose he may procure an 
exercise book, ruled both ways of the page, with lines about a quarter 
of an inch apart. The hours and volumes in cubic inches should then 
be set off exactly as in the diagrams given in the preceding pages. 
Omitting the experiments on the measurement of the carbon dioxide 
gas evolved by weighing the apparatus, the student should commence 
by making duplicate tests with the same yeasts, in order to gain the 
requisite accuracy and practice in working. The experiments described 
in the 264th and following paragraphs, or as many of them as practi- 
cable, should be performed. It is recommended that 25° C. be adopted 



176 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



as the standard temperature throughout the experiments, instead of 30° C 
Practical directions follow. 

278. Apparatus requisite. — Water-bath to hold yeast bottles, 
sets of yeast testing apparatus, pneumatic troughs, bunsen burner and 
automatic temperature regulator, thermometer, &c. 

The water-bath may conveniently consist of a large iron saucepan (or 
Scotch "goblet"); to this should be attached a side-tube, by means of 
which the height of the water in the bath may be regulated : for 
description of this very useful device see paragraph 471, chapter XX. 
Regulate the height of the water in the bath, so that the yeast bottles, 
when charged, shall be on the verge of floating, the surface of the liquid 
in the bottle will then be about an inch below that of the water in the 
bath. During very hot weather, and particularly when working at the 
lower temperatures, it is advisable to have a stream of cold water run- 
ning through the bath. For this purpose, lead the end of a piece of 
bent tube, connected with a water tap, into the bath over the top, on 
the opposite side to side-tube before referred to : turn on a small stream 
of water through this bent tube, scarcely more than what would cause 
rapid dropping from its end. Water will then be continually finding 
its way in through this tube, and making its exit through the side- tube : 
thus lowering the temperature when necessary. Do not let the stream 
from this cold water tube impinge directly on either of the yeast bottles. 

The construction and arrangement of the yeast testing apparatus and 
pneumatic troughs have already been sufficiently fully described. 

279. Automatic Temperature Regulator. — The bath is 

warmed by means of a bunsen burner arranged underneath, and, in 
order to maintain the temperature at any desired point, an automatic 
regulator is employed. As an unvarying temperature is necessary for 
several other chemical operations, a detailed description of such an auto- 
matic regulator is given. There are several of these instruments made 
and sold under various names; but for general purposes the author prefers- 
the following modification, designed by himself, and shown in figure 24.. 



TECHNICAL RESEARCHES ON FERMENTATION. 



177 




/ 



b 



\ 



a 



FIG. 24. — AUTOMATIC TEMPERATURE REGULATOR. 

The instrument consists of a bulb, a, about 4 inches long, and J inch 
in diameter ; to this is attached a stem, b b, about a J inch diameter, and 
6 inches long. This stem bends over at the top, and is connected with 
a U-tube, c d e, J inch diameter, in which are blown two bulbs as figured,. 
//, about f inch diameter. The one end, c, of this U-tube is closed with 
a stopper, g, which is ground in with extreme accuracy. From the centre 
of the bottom of this stopper, a hole is bored upwards for a short distance, 
which hole joins another bored inwards through the side of the stopper ; 



178 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

this hole, therefore, affords a passage up through the bottom of the 
stopper and out through its side. A corresponding hole is bored through 
the side of the neck, c, of the U-tube, so that if the stopper be turned 
so that these two holes coincide, a passage is provided from the U-tube 
to the exterior ; this exit may be closed at will by slightly turning this 
stopper, g. To the other end, e, of the U-tube, c d e, is sealed in a bent 
tube, hij ; below the joint, e, this tube, h ij, is made much finer, 
having its smaller end, /, -^ inch in diameter, and ground obliquely as 
shown in the figure. Below the joint, e, but as near to it as possible, 
.an outlet tube, k I, is sealed into the U-tube, c d e. This completes the 
regulator ; the method of using the instrument, and its principle, may 
be conveniently described together. 

By means of a screw-clamp carried on a retort-stand, or any other 
suitable holder, fix the regulator upright, and so that the bulb, a, 
shall be wholly immersed in the water of the bath, and the ends of 
the tubes, li and 7, projecting over its side. The regulator should 
be perfectly rigid when fixed ; the clamp is best screwed on to the 
stem, b b. Connect up h by india-rubber tubing with the gas tap, 
and join up I to the bunsen burner. Partly fill the U-tube, c d e, 
with carefully cleaned mercury through c. Turn on the gas and 
light the bunsen burner, then continue the filling of c d e with 
mercury until the level rises sufficiently high in the limb d e, to very 
nearly close the end of jet j. The quantity of mercury added should be 
sufficient to just begin to shut off the supply of gas to the bunsen ; it is 
evident that then a very slight rise in level of the mercury would either 
considerably diminish or entirely shut off the gas from the burner. 
Next heat a little india-rubber sufficiently to liquefy it ; smear the 
stopper, g, and its neck with this liquid, taking care to preserve a clear 
passage through the hole in the stopper. Next pour some of the 
strongest alcohol obtainable through c, until the bulb, a, its stem, b b, 
and the part of c are completely filled with alcohol. Insert the stopper, 
g, so that the hole through it is open ; the excess of spirit escapes. It 
sometimes happens, in filling the instrument with spirits, that the 
level of the mercury in the U-tube is disturbed, the spirits floating 
on its surface at c, forcing up the level in e sufficiently far to entirely 
close the jet, j. Should this happen, the mercury must again be adjust- 
ed by removing a small drop by means of a fine pipette. Having made 
these adjustments the instrument may be regulated for any desired 
temperature. Place a thermometer in the bath, so that the height of 
the mercury can be easily read, and so that its bulb does not touch the 
bottom. Suppose it is wished to maintain the bath at 25° C, turn the 
stopper, g, so that the hole is open, and light up the burner. The gas 
finds its way through the tubes, h ij Jc I, in the directions of the arrows. 
As the temperature of the water in the bath increases, so does that of 
the spirits in a. With a rise in temperature the alcohol expands, and 
a small portion finds its way out through the hole in the stopper, g. 
Watch the thermometer carefully, and when the temperature stands at 
about one-tenth of a degree below 25° C, turn the stopper, g, so as to 
close the hole through it. The spirits, in expanding, now find no means 
of escape, and so drive down the mercury in c d, causing a corresponding 



TECHNICAL RESEARCHES ON FERMENTATION. 179 

rise in d e ; the consequence is that the jet, j, is either wholly or partly- 
closed, and the gas either completely or partly shut off from the burner. 
The bunsen used should have a cap of fine wire gauze fastened on to it, 
.so as to prevent its lighting at the bottom when the flame is turned 
very low. A small pin-hole burner should be fixed to the bunsen, and 
fed from an independent supply, so as to re-light it should the regulator 
turn it completely out ; this " pilot " burner must be turned down so as 
to only give a flame about J inch high, and should not be able to appre- 
ciably warm the bath. The regulator will at first most likely shut off 
the gas completely ; the bath will then cool slightly, and as the alcohol 
in a contracts, the level of the mercury in d e will fall, and so the jet, j, 
will once more be opened, and a passage of gas to the burner permitted. 
With this regulator properly set, the temperature keeps between two 
•extremes that after a short time closely approach each other ; in fact, 
the mercury so adjusts itself as to partly close the aperture j, allowing 
just sufficient gas to pass to keep the bath at a constant temperature. 
The end of j" is cut obliquely in order to prevent the mercury sticking 
to it, and so acting irregularly. Alcohol is used in a instead of air, 
because it is not affected by changes of atmospheric pressure ; when tem- 
peratures above the boiling point of alcohol are required, the instrument 
must be used with air, or else some liquid having a sufficiently high 
boiling point. Alcohol is preferable to water, because it has a much 
higher co-efficient of expansion, that is, for an equal rise in temperature 
it expands much more. With the instrument set as described, it should 
maintain the temperature closely at 25° C. ; if it should be found to be 
somewhat higher, the instrument may be made more delicate by adding 
a very little more mercury, or it may be shut off somewhat earlier; 
thus, if it be found to give a constant temperature 0*4° over that at 
which the stopper, g, is shut off, then all that is necessary is to always 
shut off at 0"4° below any temperature that may be required. Should 
the temperature be too low, it may be raised slightly by carefully turn- 
ing the stopper, g, momentarily, until the slightest drop of spirits oozes 
out ; if the temperature is too high, the bath must be cooled down, and 
again regulated on the rising temperature. If the bath is required to 
be used for several days at the same temperature, a]l that is requisite is 
to turn off the gas when the day's work is done ; as the bath cools, the 
mercury rises in c d through contraction of the alcohol ; the bulbs, //, 
are provided in order to allow of this rise, without its altering the 
regulator. When the bath is next required, simply turn on the gas, and 
the regulator, without any attention, will maintain the temperature at 
the point for which it was adjusted. The advantage of this form of 
regulator is that it keeps perfectly constant for a very long time, as 
there are no parts to shift, or places from which leakage may occur; the 
stopper, g, smeared with melted india-rubber, is perfectly air-tight. Grease 
will not answer instead of india-rubber, as it is dissolved by the alcohol. 
280. Method Of Testing. — To make one or more experiments 
proceed in the following manner : — First, carefully enter in the note 
book the particulars of each experiment, and number them : place 
corresponding numbers on the bottles. Regulate the water-bath at the 
^desired temperature, and place in it a flask containing sufficient water 



180 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

for the experiments that are to be made. Having cleaned the whole 
apparatus, arrange in order the generating bottles required, and weigh 
out and introduce into them the yeast mixture or other substance to be 
fermented. Next weigh the yeast, taking care that a good representa- 
tive sample is obtained. With pressed yeast, cut a thin slice off the 
middle of the slab, avoiding dry and crumbling fragments. Brewers' 
yeast must first be well stirred, and then weighed out in a counterpoised 
dish. Break up the pressed yeast carefully in a small evaporating basin, 
with some of the water which has been raised to the right temperature ;, 
for this purpose an india-rubber finger stall placed on the finger is 
useful. Pour the yeast and water into the bottle ; rinse the basin with 
the remainder of the six ounces of water. As rapidly as possible, intro- 
duce each sample of yeast, to be tested, in its respective bottle in precisely 
the same manner. Having introduced the yeast, yeast mixture, or other 
substance, and water, into the respective bottles, gently shake each bottle 
so as to thoroughly mix the ingredients; then tightly cork each bottle, 
and arrange the apparatus as shown in figure 15, given at the commence- 
ment of the chapter. Remove the glass stopper at d, and suck out the 
air from the apparatus until the water rises in the jar, /, somewhat above 
the zero, then again insert the glass stopper. Pinch the india-rubber 
tubing on one side of d so as to make a slight opening, and thus permit 
air to enter ; in this way lower the water in / until its level exactly 
coincides with the zero. Perform this operation as rapidly as possible 
with all the apparatus being used, and note the exact time in the note 
book. As the fermentation proceeds, the surface of the water in the 
jars will become lower, and in this way a measure of the amount of gas 
yielded is obtained. At the end of every half-hour or hour from the 
commencement, read off the volume of gas, and enter the same in the 
note book. When the jars are nearly full of gas watch them carefully, 
and as soon as the 100 cubic inches mark is reached withdraw the plug 
at d, blow into the jar for a few seconds so as to displace carbon dioxide 
through the bottom, and then suck out the air until the water again 
rises to the top of the jar, re-insert the plug, and rapidly adjust the sur- 
face of the water to the zero. This operation should last only a very 
short time, and does not practically affect the results that are being 
obtained. The readings may be taken for from, say, two to six hours ; 
or if wished until the action ceases. These directions apply equally to 
the ordinary use of the apparatus for testing the strength of yeasts. 

281. Preparation of Yeast Mixture.— It is essential that the 

substances composing this mixture be thoroughly mixed. The following 
is the best mode of procedure. First, dry the substances at a gentle heat 
(100° C.) In the laboratory, this is done by placing them in a hot-water 
oven ; then finely powder each in a mortar, and weigh out the right quan- 
tities. Then thoroughly mix the first four ingredients ; afterwards add 
the fifth, and again mix ; then add the sugar little by little, mixing between 
each addition. In this way an equal composition of the mixture through- 
out is assured. Pinzel's sugar crystals (coarse crystalline coffee sugar) is 
almost chemically pure ; failing this, the best loaf sugar may be used. 

The pepsin necessary for the experiments may be obtained from the 
chemist. 



TECHNICAL RESEARCHES ON FERMENTATION. 181 

The malt wort may be prepared by infusing coarsely ground malt 
with ten times its weight of water for two hours at 65° C. : it is then 
filtered, diluted down with water until at the right density. 

In experiments with flour, the flour and part of the water should first 
be placed in the generating bottle, and thoroughly shaken before the 
addition of yeast. 

The starch is gelatinised by allowing it to stand in a small beaker, 
with some water, for about five minutes in the hot water-bath, stirring 
thoroughly meanwhile. 

The experiments on flour infusion, in which the sugar is determined 
before and after the fermentation, are very important, but had better be 
postponed until the student has proceeded with his studies of analysis. 

In the temperature experiments, the tests at the same temperature 
should be made on the same day, and the complete series with as little 
interval as possible between. 

In addition to the experiments described in this chapter, many others 
will suggest themselves to the practical baker : these he may arrange for 
himself, and use the yeast apparatus as a means of measuring the evolu- 
tion of gas, under any conditions that may be of interest to him. The 
student will do well, in addition, to perform the following series of tests. 

282. Keeping Properties of Different Yeasts.— Procure 

samples as fresh as possible of different pressed, brewers, and patent 
yeasts. Test immediately after procuring them ; then store in a cool 
cellar, and test each sample on successive days until they are capable of 
setting up little or no fermentation. To ensure perfect accuracy it is 
well to keep each sample of yeast in a weighed vessel, any loss by 
evaporation may then in the case of the liquid yeasts be made up each 
day by the addition of distilled water. The pressed yeast may be kept 
in a stoppered bottle, or preferably, the portion for each estimation 
should be taken from the interior of the mass ; as a check, moisture 
should then be estimated in the yeast each day. 

283. Use of Testing Apparatus without Temperature 

Regulator. — In the foregoing descriptions given it has been directed 
that the yeast bottle stand in a water-bath regulated by an automatic 
temperature regulator. While such an arrangement is extremely use- 
ful, it is not absolutely necessary. For actual bakehouse use the follow- 
ing plan answers well. Select a place somewhere near the oven, where 
the temperature is pretty constant, and, if possible, between 70° and 
80° F. Arrange on a shelf, clamped to the wall, a saucepan sufficiently 
large to take the yeast bottles, and fix the trough for the graduated jar 
in position. The saucepan will have to be raised sufficiently high by 
means of blocking ; this should be properly done at the outset, as the 
apparatus should remain there permanently. When about to use the 
apparatus, first of all fill the saucepan with water at the desired tem- 
perature F., and then make the estimation. A warm place being 
chosen, the water in the saucepan will not fall very much in tempera- 
ture during the time necessary for carrying out the experiment. This 
method of using the apparatus applies more particularly to yeast testing 
than to the more delicate experiments described in the preceding pages. 



182 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



CHAPTER XII. 

MANUFACTURE AND STRENGTH OF YEASTS. 

284. For baking purposes three commercial varieties of yeast are 
employed, namely, Brewers', Continental Compressed, and " Patent "' 
yeasts. These latter may again be subdivided into malt and hop yeasts 
as used in England, and the Scotch flour barms. Descriptions follow of 
how these yeasts are manufactured. 

Brewers' Yeast. 

285. In the chapter on fermentation, an account is given of the- 
appearance of an actively fermenting tun of brewers' wort. The brewer' 
first treats his malt with water at a temperature of about 65° C. for 
about two hours, more or less ; during that time the starch of the malt 
is converted into dextrin and maltose. The liquor is then allowed tO' 
drain from the grains, or husks of malt, and is transferred to a copper- 
in which it is boiled with hops : the hops are removed and the wort 
rapidly cooled, either by being exposed to the air in shallow open coolers, 
or poured over a specially arranged apparatus, consisting of a series of 
pipes through which cold water is passing, and which is termed a refrigera- 
tor. This cooling must be done as rapidly as possible, as a tempera- 
ture of about 30° C. is particularly suited to the rapid growth and 
development of disease ferments. On the wort being cooled to 18 or 
19° C, (65° F.), about one one-hundred and fiftieth part of its weight 
of yeast from a previous brewing is added. Eermentation sets in, and 
after a time yeast rises to the surface, and is skimmed off. The first is 
rejected because any lactic ferments or other bacteria that may be 
present are, from their small size, floated up to the surface with the yeast 
on its first ascent. At the time when the fermentation is most active 
and vigorous, the best yeast is being produced. As fermentation 
slackens, cells are thrown to the surface which have been grown in a 
comparatively exhausted medium. Such yeast is weak, and possesses 
less vitality. For their own pitching purposes, the brewers reserve the 
middle yeast. Too frequently that sold to bakers is the refuse yeast 
from either the beginning or ending of fermentation. Bakers who use 
brewers' yeast should insist on being supplied with that equal in quality 
to what the brewer himself uses for starting fermentation. He may 
fairly be asked to pay somewhat more for this ; but to the baker, of 
yeast, above all things, the best is the cheapest : one spoiled batch of 
bread will cost the difference between good and bad yeast over probably 



MANUFACTURE AND STRENGTH OF YEASTS. 183 

many weeks or months, to say nothing of the injury done to the baker's 
reputation with his customers. The yeast, when skimmed, should be 
stored in shallow vats, so as to admit of free access of atmospheric 
oxygen. 

Brewers' yeast is much used in the production of what is called 
" farmhouse " bread : it is supposed to produce a sweeter flavoured loaf 
than do other varieties. On the other hand, brewers' yeasts darken the 
colour of bread. Flavour is essentially a question of individual taste 
rather than science, consequently the opinion of the chemist, like that 
of every one else, simply depends on the delicacy and experience of his 
palate. Venturing an individual opinion, the author has tasted some 
exceedingly well flavoured bread made from brewers' yeast, assisted by 
compressed yeast • but on the other hand, the bread which of all others 
he prefers has been made with yeasts of other kinds. With however good 
a yeast, high-class breads cannot be produced from low grade flours. For 
bakers' purposes, brewers' yeast is weak, and if used alone must be em- 
ployed in considerable quantity. It is apt when freely used to impart a 
bitter taste to the bread : this may be in part obviated by washing the 
yeast, but even then it is exceedingly difficult to remove the bitter taste. 
The author has been informed that London brewers' yeast merchants 
collect the yeast from various breweries, and wash it by stirring it up 
with a dilute malt wort; it is then allowed to settle, and the supernatant 
liquid poured off. To a certain extent this removes the bitterness. From 
samples of brewers' yeast, as supplied by London yeast merchants tO' 
bakers, that the author has examined, he cannot speak very highly of 
this class of yeast. Compared with yeasts obtained direct from good 
breweries, the yeast merchant's yeast has been much weaker and more 
impure. Particularly in summer time brewers' yeast is found to be 
very unreliable and uncertain in its actions. Even those bakers 
who prefer brewers' yeast, when they can procure it good, find them- 
selves compelled to resort to compressed yeast during the hot summer 
months. 

In selecting a brewers' yeast for bakers' purposes, scrupulously avoid 
those breweries where large quantities of sugar or other malt substitutes 
are used instead of malt itself. Such brewing mixtures contain a de- 
ficiency of appropriate nitrogenous matters, and so the yeast produced 
is weak and impoverished through ill nourishment. 

In some breweries, the beer is allowed to finish its fermentation in 
large casks, arranged so that the bung-hole is very slightly on one side : 
the yeast slowly works out of the bung-hole and flows in a shallow 
stream down the outside of the cask until it reaches the bottom, when 
it drops in a gutter arranged to receive it. A number of these casks are 
usually arranged side by side, and connected together by a pipe at the 
bottom ; they are consequently technically termed " unions." The one 
gutter receives the yeast from the series of unions and conveys it to the 
proper receptacle. The yeast from these unions is found to make far 
better bread than that skimmed from large fermenting tuns. The 
reason is that the yeast gets thoroughly aerated during its flow down the 
side of the cask. For baking purposes, the thorough seration of yeast 
is essential. 



184 CHEMISTKY OF WHEAT, FLOUR, AND BREAD. 

286. Microscopic Examination of Yeast. — This operation 

requires a fair amount of experience before a trustworthy judgment can 
be formed. In microscopically examining yeast, there are two distinct 
points to be observed. First, the presence or absence of disease fer- 
ments, bacteria, &c. ; second, the appearance of the yeast cells them- 
selves. For satisfactory work, a power of six or eight hundred diameters 
is necessary : the objective must be a good one, giving not only magni- 
fication, but also clear and accurate definition. The author uses a 
microscope in which several objectives are fastened to one " nose-piece," 
so that the powers may be changed instantaneously, without the trouble 
of unscrewing the one objective and then replacing it by another. 
Working with this instrument, it is his practice to first examine the 
yeast with a magnification of about 440 diameters, and then, having 
seen the aspect of a fairly large field, he observes more closely a few 
typical cells with a magnifying power of about 1000 diameters. Thorns, 
whose microscopic researches on bakers' yeasts are so well known to 
bakers, employs an immersion lens, giving him a magnification of about 
2500 diameters ; but it is doubtful whether any except microscopists 
of long experience could work with such high powers to advantage. 

First, with regard to the presence or absence of foreign ferments. The 
fewer of these the better the yeast. A yeast for bakers' purposes needs 
to be judged by a somewhat different standard to that adopted by the 
brewer. To the latter, the presence of lactic or butyric ferments or 
other disease organisms means that during the period the beer is stored 
before it is all consumed, there is ample time for changes to go on which 
will result in either a marked deterioration, or spoiling, of the beer. 
But if this change does not make itself perceptible until, say two or 
three weeks have elapsed, it follows that, as bread is fermented, baked 
and eaten within about three days, that under ordinary circumstances 
such changes cannot take place in bread. This explanation is necessary, 
because it is well known as a matter of fact that many bakers do suc- 
ceed in producing very good bread, who use a yeast in which there is 
frequently an abundance of foreign organisms. It will in such cases, 
however, be found that they take special precautions which serve to 
prevent an injurious action of these during fermentation. Summing 
np, yeasts may be used by bakers which could not possibly be employed 
by the brewer, because the fermenting process of the former is so much 
shorter ; nevertheless an excess of disease ferments may set up injurious 
action even during the time of panary fermentation unless special pre- 
cautions are taken. It is consequently safely laid down that the fewer 
of these foreign organisms the better. The presence or absence of dis- 
ease ferments affords a valuable indication as to the previous history of 
the yeast, apart from their own specific action on the dough. A yeast 
largely contaminated with foreign organisms has been badly made : un- 
sound malt will very likely have been used for its manufacture, and the 
whole process of fermentation conducted in dirty vessels. As in a 
brewer's yeast, the presence of disease ferments tells us this of its pre- 
vious history, the yeast should be condemned, because when carelessly 
produced under such unfavourable conditions, the yeast itself is likely 
to be unsound, or at least very uncertain in its quality. 



MANUFACTURE AND STRENGTH OF YEASTS. 185 

Secondly, with reference to the yeast cells themselves, the actual 
shape of the cells will vary with its origin. Ordinary English brewers' 
yeast consists of round cells, but Burton yeast is oval ; so also is that 
in other districts where very hard water is used. With any yeast, the 
cells should be about equal in size ; not irregular, with some very large 
&nd others small. The cells should be isolated, or at most only 
attached in pairs : where they occur in large colonies, the yeast is too 
young, and has not had time to thoroughly mature. The cells should 
appear plump and not shrunken. The cell walls should be of moderate 
thickness : if very thin the yeast is too young, and has not attained 
maturity ; on the other hand, very thick integuments denote an old, 
worked-out yeast. Thin cell walls may also be due not only to very 
young yeast, but also to the yeast being over-kept long enough for the 
breaking down of the walls to have commenced : under these circum- 
stances, examine the sample very carefully for free sporules floating in 
the liquid : these are small round globules, requiring careful examination 
for their detection. They are produced by the absorption of the walls 
of the cell, and the consequent setting free of its contents. Should the 
yeast contain any considerable number of these, it must be taken as 
evidence that the cell walls are either naturally excessively delicate and 
thin, or that it has been kept long enough for the cells to have com- 
menced breaking down. As in breadmaking, yeast does not bud or 
reproduce, but does its work in virtue of the energy and vitality of the 
original cells introduced, it is in the highest degree important that 
these cells should be strong, healthy, and as far as is possible with full 
maturity, removed from the state in which the cell walls break down, 
and set free the immature sporules, which must require some time 
Ibefore they can have vigorous fermenting power. The contents of the 
cells should show slight granulations : their entire absence may arise 
from the yeast being too fresh, and only just skimmed, or from the cells 
being sufficiently old for the interior protoplasm to have broken down 
into a watery mass. In the former instance the contents will be 
watery throughout ; in the latter, immature sporules may be seen float- 
ing within the cell : these, on careful examination, may be distinctly 
seen to possess the Brownian movement : if so, the yeast is far gone, 
and will be found weak and exhausted for bread making. Each cell 
should have one, or at most two, vacuoles ; but when placed in a drop of 
clear beer wort on the slide, the fluid should rapidly penetrate the cell 
walls, causing the contents to become lighter, and the vacuoles to 
disappear. These changes occur but slowly in old cells that have been 
worked for a long time. For an admirable series of illustrations of the 
appearance of yeast under the microscope the reader is referred to 
Faulkner and Robb's translation of Pasteur's "Studies on Fermentation." 

In order to facilitate comparison, yeast, various disease ferments, 
starch, and other impurities associated with yeast are shown together in 
the following figure : — 



186 



CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 




FIG. 25. — yeast AND its impurities, (after Belohoubek.) 



a, a, Large grains of wheat starch ; a', broken grain of wheat starch ; a", wheat starch ; b, b, grains 
of wheat, rye, or barley starch partly transformed by the action of diastase ; c, c, small grains of 
starch of the above-mentioned grains ; d, d, yeast cell (saccharomyces cerevisice), with one vacuole ; 
e, e, yeast cells of the same species, with a greater number of vacuoles ; /,/, yeast cells, same species,. 
with small buds ; g,g, same with larger buds (young cells) ; k, h, yeast cells, with abnormal vacuoles ; 
i, z, dead yeast cells, same species ; k, k, yeast cells, same species, in the vacuoles of which are 
swimming small particles of protoplasm ; /, /, yeast cells (sacckaromyces exigiais) ; w, trt, cells of 
mycoderma aceti; n, n, lactic ferments ; 0, o, bacteria of the vibrio class ; /, p, bacterittm termo ; 
q, q, acetic acid ferment ; r, r, various sphcero-bacteria ; s, s, gluten cells of maize ; t, hair of wheat. 
Magnified 380 diameters. 



Sketches will follow of different yeasts examined by the writer, but 
these, as has been already mentioned, are simply fac-similes of such 
studies as should be made by the student during the course of his work, 
and entered in his note-book. This form of illustration has been adopted 
in order to thus serve as a guide to the student. 

For the examination of yeast, under the microscope, dilute it down 
with water until so weak as to simply give a milky appearance to the 
water, put a minute drop on a slide, and then gently place on a cover. 
Note the size, shape, and internal appearance of the yeast cells, also 
search the field carefully for foreign ferments. 



MANUFACTURE AND STRENGTH OF YEASTS. 



187 




FIG. 26. — brewers' yeast. Different specimens magnified about 440 diameters. 
The sketches for the above engraving were made in the summer, and 
represent samples of brewer's yeast during practically the hottest 
weather of the year. The specimens marked a and b w T ere taken from 
two London samples of yeast, as sold to London bakers by yeast mer- 
chants. A considerable number of disease ferments are present in both, 
marking them as being in an unhealthy condition. It is to be feared 
that often sufficient care is not taken for the storage and preservation 
of yeast, especially during the hot weather, by those who collect brewers 7 
yeast for redistribution among bakers. On examining these two samples,, 
the writer procured, for purposes of comparison, some yeast from one 
of the neighbouring Brighton breweries ; this is figured in section c. It 
was found to be far away purer than either of the London samples, one 
or two bacteria are shown in the sketch, but there were several micro- 
scopic fields that contained no foreign ferments whatever. In general 
aspect, the cells of section c were firmer in outline, the walls being thicker, 
while the interior matter showed more distinct and darker granulations. 
It should be added that in these sketches the estimated magnification is 
only approximate. In every case where it is wished to ascertain exact 
dimensions, the eye-piece micrometer should be called into requisition. 

Manufacture of Compressed Yeasts. 

287. These yeasts are now so widely and successfully used, that some 
account of their origin and mode of manufacture claims a place in this 
work. The author frequently receives letters from bakers asking him 
to furnish recipes for the production of a good compressed yeast : from 
these it is evident that many bakers know very little as to the actual 
manner in which compressed yeasts are prepared for the market. These 
yeasts find their way into this country from France, the Netherlands, 
and Germany. They are not, as has been stated, low or bottom yeasts 
of lager beer fermentation, but are distillers' yeasts, and are formed as 



188 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

the principal product in the manufacture of spirits from malt and raw 
grain ; the spirits being used to an enormous extent in the manufacture 
of liqueurs, perfumes, wine, and brandy. This manufacture can only be 
successfully conducted on a very large scale, and cannot be imitated by 
the baker who simply wishes to make yeast for his own consumption. 

Mr. Bischof, London, the importer of Encore yeast, has kindly fur- 
nished the author with an account of the processes employed in the 
manufacture of that yeast. The Encore stands with others in the 
highest class of imported yeasts ; therefore, a description embodying 
the mode of its production may be taken as a type of the methods 
employed generally by the best distillers in yeast manufacture. It is 
obvious that any extended description of the production of compressed 
yeasts is a distillers' rather than a bakers' question, therefore the 
following account gives the principles rather than the details of the 
various processes employed. It should further be mentioned that in 
addition to the outline supplied by Mr. Bischof, the author has incorpo- 
rated information and experience gained from other sources. Distillers 
employ, in the preparation of their mash, a mixture of malt and raw 
grains : the latter consist principally of barley, rice, degermed maize, 
and rye. The latter of these, in the mixture, produces a wort well fitted 
for a healthy growth of yeast. To a great extent the particular raw 
grain selected depends on their relative cheapness from time to time ; 
but where the distiller wishes to find a market for his yeast, as well as 
his spirit, it is essential that only the best and soundest variety of grain 
be selected. The raw grain mixture is first mashed at a temperature 
commencing at from 50° to 60° C. (122° to 140° F„), and gradually 
increased to from 65° to 70° C. At the end of two or three hours the 
malt is added to an extent of from one seventh to one quarter of the 
whole of tne grain used ; the mashing is then continued until all the 
starch has been converted into maltose. One point of difference between 
ordinary distillers' and brewers' mashes is that the latter find the 
presence of lactic ferments in small quantity to be an advantage, as the 
subsequent fermentation is consequently more energetic and complete, 
resulting in a larger yield of alcohol. Distillers therefore frequently 
allow their malt to lie until lactic ferments have developed in consider- 
able numbers on the grain. This does not, however, apply to those 
distillers who make the production of yeast their principal object, as 
they do all they can to absolutely prevent lactic fermentation. Distil- 
lers who simply wish to produce spirits do not trouble to skim off their 
yeast, but place mash and yeast together in the stills. The saccharified 
mash is next cooled by refrigerators, and fermented by the addition of 
mother yeast. As the fermenting operation is performed for the purpose 
not only of producing alcohol but also the growth of yeast, it should be 
conducted so as to induce a healthy development of yeast. For this 
purpose the wort should be well aerated, being " roused " from time to 
time : the fermenting tuns should be sufficiently shallow to expose a 
large surface to air. At the time when the fermentation is most ener- 
getic, the yeast is skimmed off the surface, and conveyed by 
wooden shoots to steam sieves, by which the husks are eliminated, the 
strained liquid passing on to the settling cisterns. When settled, the 



MANUFACTURE AND STRENGTH OF YEASTS. 189 

surface liquid is drained off and sent for distilling purposes, and the 
yeasty sediment mixed with starch, and put into the filter presses, which 
squeeze out all the liquid, leaving a dough-like paste, which when 
sufliciently dry, is packed in bags and packets, and is ready for distribu- 
tion to wherever it may be needed. 

Yeast, from its peculiar slimy nature, cannot be pressed well — hence 
the addition of starch, which permits the removal of more of the liquid 
from the yeast. Absolutely pure yeasts do not keep so well as the 
same yeasts with an addition of from 5 to 10 per cent of starch. In 
high-class yeasts the quantity added is about 5 or 6 per cent. Starch is 
undoubtedly at times added to yeast in large excess; it then becomes an 
adulterant : this fraud is, however, readily detected by treating the 
sample of yeast with iodine. For this purpose, break up a little of the 
yeast with water in a test tube, add some tincture of iodine, and shake 
up ; the starch on standing will more or less separate out as a dark blue 
layer at the bottom of the tube. One of the best tests for starch 
adulteration is the yeast apparatus ; if the sample gives off a low pro- 
portion of gas, that is a proof either of the yeast being weak or else con- 
taining large quantities of foreign matter ; to the baker, both these 
come much to the same thing. A good sample of compressed yeast has 
the following characteristics — it should be only very slightly moist, not 
sloppy to the touch ; the colour should be a creamy white ; when broken it 
should show a fine fracture ; when placed on the tongue it should melt 
readily in the mouth ; it should have an odour of apples, not like that of 
cheese ; neither should it have an acid odour or taste. Any cheesy odour 
shows that the yeast is stale, and that incipient decomposition has set in. 

Viewed under the microscope, compressed yeast consists of somewhat, 
smaller and more oval cells than those of brewers' yeast. In the best 
varieties are found only traces of foreign ferments, other brands contain 
them in large numbers. The yeast cells themselves should possess the same 
characteristics as have already been described while treating brewers' 
yeast. The following sketch was made from a sample of compressed yeast. 
The cells were found, on measurement, to have the following dimensions : — 
Longer diameter ... 10 mkms. = 0-0004 inch. 

Shorter diameter ... 7*6 mkms. = 0-0003 „ 

Diameter of round cells 7*6 mkms. = 0*0003 „ 



190 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 




fig. 27. — continental pressed yeast, magnified about 440 diameters. 

The sample in question was remarkably free from disease ferments, 
one only being seen in the field sketched, while several fields showed no 
foreign organisms whatever. The granulations show very distinctly. 
The yeast in question was a very pure one, and yielded exceedingly 
good results when subjected to strength tests. 

In general character, the compressed yeasts are steady and trustworthy 
in their action; they produce sweet, well-flavoured breads, to which, 
when in good condition, they do not impart any yeasty taste. Their 
good qualities stand out most distinctly in summer time, when other 
yeasts so frequently fail entirely to produce a satisfactory loaf of bread. 
Their being produced in such large quantity causes their manufacture 
to be entrusted to men who bring the highest skill that practical ex- 
perience and science can furnish to bear on every detail of manufacturing- 
processes. The many good properties of compressed yeast lead it to be 
safely indicated as the yeast of the future. 

" Patent," or Bakers' Home-Made Yeasts. 

288. Some of the best, and at the same time some of the worst 
bread the author has ever tasted has been made with, what is commonly 
termed by the baker, " patent " yeast. This is just what any one 
familiar with the delicate nature of yeast as an organism would be led 
to expect. Brewing, whether considered as a science or an art, is a 
subject of which the average baker, among even those who make their 
own yeast, knows little or nothing. On the other hand, the continental 
manufacturers who produce pressed yeasts for the bakers' special use are 
men of the highest scientific education, who have made yeast manu- 
facture, on a sufficiently large scale to permit them to spend enormous 
sums on the most efficient plant, their life study and business. In the 
majority of instances, the baker's other business engagements prevent 



MANUFACTURE AND STRENGTH OF YEASTS. 191 

his giving yeast-making anything like adequate attention, the conse- 
quence of entrusting this operation to unskilled and indifferent hands is 
that a most irregular and unsatisfactory product is yielded. For these 
reasons a number of bakers find it pays them better to buy their yeast 
of the skilled and professional manufacturer, rather than depute the 
task of making it to an ignorant and prejudiced journeyman. Still 
there is no reason why a baker should not be able to make a thoroughly 
good and satisfactory yeast for himself. It is only necessary that he 
shall bring to bear on its production the following requisites : — sound 
materials, proper manufacturing apparatus, knowledge of the principles 
of fermentation, practical experience of brewing, and lastly, constant 
attention and supervision. As already stated, bakers' yeasts may be 
divided into two varieties — malt and hop yeasts as used in England, and 
flour barms as employed in Scotland. 
289. Bakers' Malt and Hop Yeasts. — These consist essentially 

of small mashes of malt and hops, fermented either by the addition of 
some yeast from a previous brewing, or allowed to ferment spontane- 
ously : the latter is known as "virgin" yeast. The hops present tend 
to prevent disease fermentations, as their bitter principle is inimical to 
bacterial growth and development. In virgin yeasts, particularly, it is 
necessary to use hops largely, and also plenty of malt ; as lactic and 
other foreign ferments flourish far better in a dilute saccharine medium 
than in a stronger one. The reader will already be familiar with the 
general outlines of the fermentation of a hopped wort : as an introduc- 
tory to directions for the preparation of patent yeast a careful study of 
the following experiment, made by the author, will be of service. The 
student will do well to repeat the experiment for himself : sufficiently 
full directions are therefore given to enable him to do so. 

Take two quarts of water and half an ounce of good hops, set these 
to boil in a large glass flask or other clean vessel ; boil for half an hour, 
and then cool down to 65° C. (149° F.) Scald out a large glass beaker, 
or failing this, a vessel of copper or enamelled ware ; wood will not 
answer well. Weigh out 12 ounces of ground malt and mix with the 
hops and water in the beaker. Maintain the whole at a temperature of 
from 65° to 70° C. (149° to 158° F.) for two hours; this may be done 
by standing the beaker in a hot-water bath. By the end of this time 
the saccharification of the malt should be complete. Have ready an- 
other glass vessel perfectly clean and scalded. Strain the wort, from 
the grains, through calico into this second clean vessel ; cool down as 
rapidly as possible to 25° C. (77° F.) In the meantime have ready a 
large water-bath, carefully regulated at a temperature of 25° C. by 
means of an automatic temperature regulator. Also thoroughly clean 
and scald six glass beakers of about 16 ounces capacity, and have ready 
glass covers for each beaker. Pour the filtered wort into these beakers, 
placing about an equal quantity in each. Label both beakers and cover 
with numbers from 1 to 6. Let No. 1 remain in the condition of plain 
wort; to No. 2 add 1 gram (15 grains) of good brewers' yeast; to No. 
3 add 0*7 gram (10 grains) of good compressed yeast. Prepare Nos. 4, 
5, and 6 in exactly the same manner, so as to form a corresponding set. 
Cover each beaker with its glass cover and stand the whole in the water- 



192 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



bath. Let the first series remain undisturbed, but serate those of the 
second by, some live or six times a day, pouring the contents of each 
beaker into a clean empty beaker, and then back again several times. 
After each aeration replace the covers and stand the beakers again in 
the bath. 

After about 24 hours examine each sample under the microscope. In 
the author's experiment, No. 1 at that time contained no yeast ; figure 
28 represents its appearance after three days. 




FIG. 28. — MALT WORT ALLOWED TO FERMENT SPONTANEOUSLY. 
Left half of field taken from ferment ; right from the same after being sown in warm " yeast mix- 
ture " for about three hours. Magnified about 440 diameters. 

The most careful examination of field after field revealed not a single 
yeast cell, while the whole liquid was swarming with bacteria ; a slight 
froth had formed on the top. The left hand side of the figure shows the 
wort as taken from the beaker, one or two grains of starch being visible. 
A portion of this wort was then sown in Pasteur's Fluid (Yeast 
Mixture) and again examined at the end of three hours, being main- 
tained for that time at 26'6° C. (80° F.) ; its appearance is shown in 
the right hand portion of the figure. (The student is recommended to 
employ a fermenting temperature of 25° C.) This result was obtained 
not merely once, but also in a complete duplicate series of experiments. 
The mode of procedure is the same as that employed by those bakers 
who are in the habit of allowing their yeast to ferment spontaneously — 
except that chemically clean vessels are employed throughout. Another 
interesting point is that although yeast was being used in the room at 
the time, and even beakers, containing actively fermenting worts, were 
standing side by side in the same water-bath, yet the loosely fitting 
glass covers were sufficient to prevent the entrance of yeast cells or 
spores into beaker No. 1 from external sources. 

Within twenty-four hours after being pitched, each sample was thus 
examined under the microscope. Nos. 2, 3, 5, and 6 were in a state of 



MANUFACTURE AND STRENGTH OF YEASTS. 



193 



vigorous fermentation. Subjoined are sketches made in Nos. 5 and 6 
respectively. 




fig. 29. — brewers' yeast, 24 hours after being sown in Malt Wort. 

Magnified about 440 diameters. 

This figure shows the yeast to be in an actively budding state. Notice- 
that buds of different sizes, d, are attached to the various cells. The 
interior of the cells is free from granulations ; a few show, however, as 
for instance c, a distinct vacuole. In the centre of one group an old or 
parent cell, a, is seen. The irregular fragment marked & is a small piece 
of cellulose from the malt. 



c> 0°° a Q^O 





fig. 30.— compressed yeast, 24 hours after being in Malt Wort. 
Magnified about 440 diameters. 



194 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



The appearance of this figure is very similar to that of the preceding 
one. Aji example of an old cell is to be seen at a, while the field gene- 
rally is occupied by new cells, perfectly free from granulation, and con- 
taining no vacuoles. In general aspect the cells are more ovoid in 
shape, and smaller, than those of the brewers' yeast. 

At the end of three days the yeasts were again examined, having been 
maintained at a temperature of 26-6° C. (80° F.) for this time ; a sketch 
was then made of No. 2 sample of brewers' yeast. 




fig. 31. 



-brewers' yeast, three days after being sown in Malt Wort. 
Magnified about 440 diameters. 



After this lapse of time the fermentation had very nearly ceased. 
Instead of observing a field covered with perfectly new cells, the ma- 
jority of which were actively budding, the aspect of the yeast is far more 
quiescent. Here and there an old cell is still to be seen, as at a. The 
new cells, however, have begun to assume somewhat the same appear- 
ance. In some of them vacuoles are to be seen, but only in a few. The 
sketch does not faithfully represent the appearance of the vacuoles, as 
these really only appear as lighter parts of the cells, and are not circum- 
scribed with a dark line, such as one has to use in sketching them in 
these figures. All the cells are more or less filled with faint, but dis- 
tinct, granulations. 



MANUFACTURE AND STRENGTH OF YEASTS. 



195 




fig. 32. — compressed yeast, three days after being sown in Malt Wort. 
Magnified about 440 diameters. 



There is at the end of this time a marked difference in appearance 
between the pressed as compared with the brewers' yeast. The vacuoles 
show much more distinctly, so also the interiors of the cells are much 
darker; the sketch shows several of parent cells, as at «, a. 

Particular attention is drawn to the fact that whereas samples Nos. 1 
and 4, which were allowed to ferment spontaneously, swarmed, after 
three days, with bacteria ; the whole of the other four specimens which 
had been sown with yeast showed, on observation, no foreign ferments 
whatever. It is possible that some may have been discovered by 
careful and systematic examination, but the main point is that, compared 
with Nos. 1 and 4, they were to all intents absent. Now, save by the 
addition of yeast, all the samples were exposed to precisely the same 
conditions ; the only conclusion to be drawn is that the presence of 
yeast growth is more or less inimical to that of foreign or disease ferments. 
The practical lesson to be learned from this is that bakers who prepare 
their own malt and hop yeasts, by sowing them with small quantities 
of pure yeast, not only induce a healthy growth of pure yeast ferments, 
but also retard the growth and development of disease ferments. The 
most probable explanation of this lies in the fact that, under the con- 
ditions of the experiment, there is a more or less acute struggle for 
existence between the two organisms, and yeast, being the more vigorous 
and hardy, grows and develops at the expense of the bacteria. 

After standing some time the vessels of yeast were covered with a 
film of mycoderma vini ; a growth which has been described in chapter 
IX. The cells of mycoderma are in appearance somewhat like elongated 
yeast cells, and are shown in figure 33. 



196 



CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 




fig. 33. — film OF mycoderma, taken from surface of sample of Compressed Yeast. 
Magnified about 440 diameters. 

Nothing has as yet been said about the difference between the series 
of beakers that were allowed to remain undisturbed, and those which 
were aerated from time to time. Before doing so it would be well to 
describe the results of determining the amounts of gas evolved by the 
respective samples on being tested in the yeast apparatus. At the time 
these experiments were made, the author was working with that older 
form in which the gas bubbled up through the water. 

After standing three days these samples of yeast were tested by 
being inserted in the testing apparatus. Half-an ounce of yeast mixture 
was taken, to this was added six ounces of the thoroughly stirred yeast. 
At the end of three hours, the following quantities of gas were found to 
have been evolved from each : — 

Cubic Inches. 

No. 1. Spontaneous ferment, undisturbed, ... ... 3*1 

No. 2. Pitched with brewers' yeast, undisturbed, ... 16 "8 
No. 3. Pitched with pressed yeast, undisturbed, ... 35*6 

No. 4. Spontaneous ferment, agitated, ... ... 3-7 

No. 5. Pitched with brewers' yeast, agitated, ... ... 18*6 

No. 6. Pitched with pressed yeast, agitated, ... ... 42-8 

The experiment shows very clearly that the agitation has resulted in 
the yeast being in every instance more vigorous in action. In the case 
of the spontaneous ferment there was a distinct, though slow, evolution 
of gas. The samples pitched with the pressed yeast had, by the bye, 
more than twice the capacity for causing the evolution of gas than had 
those which were pitched with brewers' yeast. It is plain that agita- 
tion in some way increases the vigour of yeast. Those students who 
have carefully read the section of chapter IX., dealing with the 
influence of oxygen on fermentation, will clearly understand the cause of 
such increase in fermentative power. 



MANUFACTURE AND STRENGTH OF YEASTS. 197 

When yeast is being made by bakers from malt and hops, although 
fermentation goes on, it is not the fermentation, as such, that is wanted. 
The change required is not the production of beer, but the growth and 
development of yeast ; hence the operation should be so conducted as to 
induce the greatest yield of yeast in the most active and vigorous form. 
Oration, or " rousing," as it is often termed, is, as will now be well 
understood, of considerable service. In brewing large quantities of 
yeast, it would obviously be difficult to aerate by pouring from vessel to 
vessel ; the same object may be served by from time to time thoroughly 
.stirring the fermenting yeast. This free access of air not only stimu- 
lates the growth of yeast, but in addition is inimical to the development 
of disease ferments ; so much so, that by careful working with plenty 
of air a yeast can be made to give moderately good results, that would 
be absolutely unusable if fermentation were conducted in closed vessels. 
It follows that yeast is better brewed in comparatively shallow and 
open tubs than in deep and closed ones. 

The careful performance throughout of this experiment will not only 
be an instructive exercise on fermentation, but will also afford good 
practice with the microscope. 

290. Patent Yeast Recipes. — The following two recipes for the 
preparation of patent yeast are quoted from the " Millers' Gazette." 

291. Virgin Malt Yeast, Eaig's "Patent."— 1 lb. hops, and 

7 imperial gallons of water are mashed for twenty minutes, then boiled 
for ten or fiteen minutes, and strained, cooled down to 170° F., and 121b. 
malt stirred into the infusion ; this, after mashing for fifteen minutes, 
has the malt grains separated or pressed out, and the liquor allowed to 
cool down to and kept at the temperature at which fermentation — 
spontaneous — (not below 76° or over 80°) — will be carried on. 

This is the Virgin Yeast. 

Fermentation will or should begin in from eighteen to twenty hours, 
and continue after that sixteen to twenty-four. When at its full height, 
take from the top half-a-gallon and place it in a close jar, in which place 
also 1 oz. or less bicarbonate of soda, and then cork air-tight and keep in 
a cool place. 

This is a store for next brewing. 

292. Banbury Patent Yeast.— 9 gallons water, \ lb. hops, \ lb. 

bruised ginger. Let these simmer three hours, then strain off, and when 
cooled to 160-170° F., stir in 7 lb. malt. Mash for three hours, strain 
and well squeeze the malt grains. When the mash-liquor has cooled to 
70-76°, start fermentation with one gallon of " patent " yeast from 
previous brewing, and add 8 lb. flour. Next clay put into a cask and 
bung close. 

This yeast is used with ferment, one quart (2J lb.) to the sack, nine 
hours from time of starting ferment to setting sponge. 

The recipes are both stated to give good results ; but the author has 
no personal acquaintance with the working of either. There are radical 
defects in the mode of procedure in each recipe. 

293. Patent Yeast, Feaist's Formula.— Mr. Feaist, of Has- 
tings, is well known as one of the largest bakers in the south of England; 



198 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

and so far as the writer knows he stands almost alone among the large 
bakers as using only patent yeast, to the exclusion of all other varieties. 
The following is a description of his method of preparing patent yeast, 
taken from " The Miller," — 40 gallons of water and 2 lbs. of sound hops 
are boiled together for half-an-hour in a copper, and then passed over a 
refrigerator, and thus cooled to a temperature of 71° C. (160° F.) The 
liquor passes from the refrigerator to a stout tub; 1-J bushels (about 
63 lbs.) of crushed malt are then added, and the mixture thoroughly 
stirred. The mash is allowed to stand at that temperature for 1J hours, 
filtered from the grains, and then rapidly cooled to 21° C. (70° F.) 
The passage over the refrigerator serves also to thoroughly aerate the 
wort. The wort is then set ; fermentation sets in, and the yeast is 
ready for use in 24 hours, but is in better condition at the end of two 
days. All fermenting tubs, and other vessels and implements used, are 
kept clean by being from time to time thoroughly scalded out with live 
steam. Mr. Feaist devotes great attention to his yeast, and his efforts 
result in the production of a first-class article. 

294. Suggestions on Yeast Brewing ; what to do, and 

what to avoid. — Mr. Feaist's quantities are larger than those 
required by many bakers, but the formula may be adopted for smaller 
brewings by taking a half, or quarter, or some other proportion of each 
ingredient. In connection with brewing, the first consideration is the 
room ; this should not be in the same part of the bakehouse as the ovens. 
Select, if possible, a room having an equable temperature of from 65 to 
70° F. Stout tubs of appropriate size should be used for brewing; these 
should be about the same width as depth. Before commencing, clean all 
tubs and implements with boiling water. The hops are better boiled in 
a copper ; iron vessels are apt to discolour them, especially if the vessels 
are in the slightest degree rusty. Let the hop liquor cool down to the 
temperature given, before adding the malt, as a temperature much higher 
than from 65 to 70° 0. destroys the diastasic power. On no account 
boil the malt : some bakers place malt and hops together, and boil the 
two, under a mistaken idea that they get more extract from the malt. 
The result is that diastasis is arrested long before the whole of the starch 
is converted into dextrin and maltose. For the same reason, fifteen 
minutes is too short a time for the mashing to be continued. The 
baker not only requires to saccharify his malt, but it is also necessary 
for him to convert as large a proportion as possible of his dextrin into 
maltose. This is hindered either by using too high a temperature, or 
mashing for too short a time. Starting with a mashing liquor at 65 to 
70° C, and mashing for from 1 \ to 2 hours gives about the best results. 
The cooling after removal from the grains, which may be washed or 
" sparged " with a small quantity more water, must be done quickly, so 
as to have the wort for as short a time as possible at a temperature of 
from 35 to 40° C, as at that temperature bacterial fermentations pro- 
ceed most vigorously. The wort at 21 '5° C. (70° F.) may either be 
pitched with a small quantity of yeast reserved from the last brewing, 
or by the addition of a small quantity of good fresh compressed yeast. 
The temperature should not be allowed to rise, during fermentation, 
much above 21 to 22° C. In summer time there is a great tendency for 



MANUFACTURE AND STRENGTH OF YEASTS. 199 

a rapid rise to set in ; this may be controlled by placing an attemperator 
in the wort, and passing a stream of cold water through. An attem 
perator consists of a properly arranged series of pipes, through which 
hot or cold water at will may be passed. Temperatures must in all 
cases be got right by actual use of the thermometer. From time to 
time, stir the fermenting wort so as to rouse or aerate it : should it 
happen to be sluggish, throw in a handful of raw flour. When the 
yeast is made, keep it freely exposed to air. In making patent yeast it 
is very poor economy to stint either malt or hops : a weak wort produces 
a much less healthy and vigorous yeast than does a strong one, beside 
being much more subject to disease fermentation. And, when made, 
the dilute yeast shows no saving, because so much more of it has to be 
taken in order to do the same work. Dealing with this topic, " Tablier 
Blanc/ 5 in the " British and Foreign Confectioner," forcibly writes, — 
" Weak worts are very liable to turn sour. I have seen 20 gallons of 
water, and 120 used, each with the same quantity of malt and hops; 
that is six times as much water in one case as in the other, and the 
result was that one gallon of the strong was found to be better than six 
of the weak. I will now close these remarks on barm-brewing with a 
maxim which is worth remembering, and should be borne in mind and 
acted on whilst making it. It is this — Water is 'not barm, therefore 
use as little of it as you can." 

295. Specific Gravity of Worts, and Attenuation.— In 

addition to taking the temperature of his worts, the brewer also tests 
the density or specific gravity of each sample. This is done as a means 
of estimating the amount of soluble extract obtained from the malt. 
The maltose and other soluble carbohydrates, yielded on mashing, in- 
crease the specific gravity of the wort. Taking the density of water as 
1000, each gram of carbohydrate in 100 c.c, or, what amounts to the 
same thing, each lb. of carbohydrate in 10 gallons of the wort, increases 
the density of the solution 3*85. Thus, suppose that a wort is found at 
15-5° C. (60° F.) to have a specific gravity of 1011-5, then 

1011-5 — 1000 

= 3 = weight in lbs. of 

3-85 6 

sugar and other solid matter in 10 gallons of the clear wort. As the 
density of a liquid varies with its temperature, all densities are best 
taken at the uniform temperature of 15 -5° C. 

The Inland Revenue Act of 1880 assumes that 2 bushels of average 
malt, weighing 84 lbs., will produce a barrel (36 gallons) of wort having 
a density of 1057. Accepting this estimate as correct, and assuming 
that the 40 gallons of water employed in the previously given recipe, 
together with the small extra quantity used in sparging or washing the 
grains, yield after loss through evaporation, 40 gallons of wort ; then 
the wort produced ought to have a density of 1038*3, which is equal to 
almost exactly 10 lbs. of solid extract per 10 gallons of wort. Working 
with comparatively imperfect methods, and in small quantities, the 
baker cannot expect his malt to yield the full extract, but as a matter 
of practice he ought at any rate to get nothing less than a density of 
1030. One of the most important sources of loss arises from imperfect 



200 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

sparging of the grains; these should be washed once, and may then with 
economy be put into a small press and squeezed dry. Of course, if with 
extra washing water, the volume of the wort is increased, then the 
density will naturally fall. Testing the density of his wort is not only 
of importance to the baker, as a measure of the degree of efficiency with 
which he is extracting the valuable matters of his malt, but is also a 
test, of the highest value, of the regularity of his work. If one day a 
wort of comparatively high density is being attained, and on another 
one of low density, something is wrong, and must be righted. The 
baker should always endeavour to have his worts at the same density 
when ready for pitching ; 1030 may be taken as a very good standard 
to work at. If it is found in practice that the densities fall below this, 
mash with comparatively less water ; if the densities run too high, dilute 
the wort with water until of the right density before pitching. The 
necessary quantity of water to add may be easily calculated, on re- 
membering that the volume of the wort is in inverse proportion to the 
■density, less 1000. Thus, supposing that the 40 gallons of wort are 
found to have a density of 1035, then 

as 30 : 35 : : 40 : 46 gallons. 
The wort will have to be made up to 46 gallons, therefore 6 gallons of 
water must be added. The quantity of wort produced should always be 
measured ; to do this, determine once for all the capacity of the fer- 
menting tubs in the following manner : — Prepare a staff about an inch 
square ; pour water into the tub, gallon by gallon, and at each addition 
put in the staff and mark on it the height of the water. This operation 
once completed, the quantity of wort made can at any time be deter- 
mined simply by plunging the staff into the tub and reading off the 
number of gallons as marked on it. 

For practical purposes, the density of a wort is best determined by a 
hydrometer, this instrument is made either of brass or glass. It has a 
weighted bulb at the bottom, and a long graduated stem ; accompanying 
the hydrometer is a tall glass jar, known as a hydrometer jar. Fill this 
jar with wort at the right temperature, and place in the hydrometer ; 
as soon as it comes to rest, read off the graduation which coincides with 
the level of the liquid ; the number gives the density. For the baker, 
the most convenient hydrometer is one graduated in single degrees, 
from 1000 to 1040. The hydrometer is also sometimes known as a 
saccharometer. 

As fermentation proceeds, the density of the liquid becomes less, and 
at the same time it loses its sirupy consistency — hence the brewer states 
it to have become " attenuated." 

296. Microscopic Sketches of Patent Yeast.— In the 

following figure are given microscopic sketches made of patent yeasts 
collected in the South of England. 



MANUFACTURE AND STRENGTH OF YEASTS. 



201 




fig. 34. — bakers' patent yeast, different specimens magnified about 
440 diameters. 

The sketches marked respectively a and b were drawn from samples 
of patent yeast, both obtained in the same town, but from different 
bakers, during the summer. The sample marked a was evidently pre- 
pared in a strong wort ; in fact, at the time of examination the yeast 
was still sweet through presence of maltose in considerable quantity, 
and had a high density. The yeast was not free from disease ferments, 
but still compared remarkably favourably in this respect with all other 
samples examined. One specially noticeable point about the sample 
was the elongated shape of the cells, some were not merely ovoid, but 
even decidedly pear-shaped. One sketched shows this peculiarity in a 
very marked manner. This yeast was at the time yielding very good 
results ; the bread was sweet and of good flavour. One is in doubt with 
regard to sample b, whether it should be termed yeast or bacteria; 
certainly these latter ferments are about as plentiful as yeast cells. 
The yeast contained very little either of maltose or hops. In fact, it 
had evidently been brewed with as little as possible of these ingredients 
employed. Readers will probably not be surprised that baker a does a 
larger trade than does baker b. The sample e is likewise of considerable 
interest • it was also taken during the summer. The baker was in the 
habit of, at the close of his yeast brewing, setting aside a portion for 
the purpose of pitching his next lot of wort. This pitching yeast was 
stored in a corked bottle. This also was a yeast brewed in a poor wort, 
although not so bad as sample b. Notice particularly, in c, the chain 
of elongated cells ; these are often noticed in yeast grown without 
sufficient aliment, and the sketch shows a striking example. 

Scotch Flour Barms. 

297. There have recently appeared two authoritative statements on 
Scotch flour barms ; the one in "The American Miller," by Thorns ; the 
•other in "The British and Foreign Confectioner," by a "Glasgow Baker," 



202 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

of whom it may be here stated that he is one of the most eminent and ex- 
perienced among the large number of practical bakers in that city. Both 
these descriptions are so important that they will best be given in full. 

298. Flour Barms, Thorns' Formulae.— "There are many kinds 

of flour barms used in Scotland, in fact all are flour barms ; but for 
the present I will treat of two of the latest and best. These are 
' Parisian Barm ' and ' Virgin Barm.' Virgin differs from Parisian 
only in being spontaneously or self-fermented. Parisian barm was in- 
troduced from Paris to Scotland, by a baker near Edinburgh, about 
twenty years ago. It is essentially a leavening ferment ; a scientific 
modification of the systems of ancient Egypt and present France. 
After its introduction to Scotland its use spread rapidly, and it alone 
is used in all the machine bread factories there, and in a number of the 
best establishments in the north of Ireland. The Parisian is easy to 
make, but easier to spoil. All that is required is skill to select the 
materials, and knowledge, founded on experience, to guide the process- 
of fermentation, which results in inert flour and water, infusions of 
malt and hops, being converted into the vital, self-propagating and 
carbonic-acid producing substance we call barm, which makes fermented 
bread light and vesiculated. 

299. " Virgin Barm : Things Required.— A 30 or 32 gallon 

tub; a small tub or vessel for malt-mashing ; 10 lbs. malt; 3 oz. hops, 
and a jar in which to infuse them ; about 40 lbs. flour, of which one- 
third should be American Spring straight and two-thirds Talavera 
wheat flour, or sound red Winter : 2 or 3 oz. salt ; 8 or 12 oz. sugar; a 
handful of flour; and about 18 gallons of boiling water. (The gallon here 
means the Imperial, holding 10 lbs. water at a temperature of 60° F.) 

300. " How to Use or Manipulate them. — Mash the malt for 

1J hours in 3 gallons of water after it has been cooled to 160° F. ;, 
infuse the hops the same time in 1 gallon of water poured over the hops 
at a boiling temperature ; then strain the malt and hop infusions into the 
barm tub ; now sparge or wash the draining malt grains with another 
gallon of water at a temperature of 1 90° or 200° F. Note, the malt grains 
are not pressed in any way, only allowed to drain. When the water has. 
about stopped running from the grains, the liquor in the tub should 
show a temperature of 140° or 146° F., then well and thoroughly mix in 
the flour with the hands. The next stage is scalding this mixture or 
thin batter with 7 gallons of boiling water, and stirring sharply with a 
stick. Begin by pouring in 2 gallons, and stirring it well up and from 
the bottom and all round, then add another 3 gallons and give more 
and sharp stirring, and finish with another 2 gallons and more stick 
work. The scalded batter is then a thick jelly ish paste. The water 
used in malt and hop infusions and sparging is 5 gallons, in scalding 7 
gallons, making in all 12 gallons. I mentioned 18 gallons because it is 
desirable to have more boiling water than required. 

30 1. " Fermentation. — The barm tub and contents are left in the 
brew-house uncovered for 21 hours or so. During that time the mixture 
undergoes several changes. The scalding water bursts a proportion of 
the starch granules of the flour, converting them into starch paste ; the 



MANUFACTURE AND STRENGTH OF YEASTS. 203 

diastase of the malt inverts or hydrates this paste into a sugar, maltose, 
and a brown, gummy body, dextrin. The mixture, after scalding, tastes 
very sweet ; in half an hour after it is sweeter, and thinner, and browner. 
These changes continue for several hours, then a distinct acid taste is 
felt. At the end of 21 hours the mixture is strained from one tub into 
another, so as to serate it. When it has cooled down to 84° F., mix in 
the salt, sugar, and a handful of flour, and keep the tub lightly or un- 
covered in a place where the now slightly fermenting mixture will not 
fall below a temperature of 80° F., or rise over 84° F. Supposing this 
is done 24 hours after brewing, then during the next 24 hours stir up 
the mixture three times — the number of times depends on the fermen- 
tation being free or sluggish — and note the heat, and at the end of the 
24 hours again strain gently from one tub to another. In another 12 
hours stir up again ; it will then be in vigorous fermentation, and will 
rise and then fall. When nearly full down, or when a lighted match 
will burn within three or four inches of the surface, remove the tub to 
a cool place. This will be on the third day after brewing. This barm 
could be used in a sponge the same day, but it is far better on the 
fourth and fifth day after brewing. 

302. " Parisian Barm.— The materials, and quantities and mani- 
pulation, are the same as for Virgin. Only in about 24 or 27 hours after 
brewing, and when the mixture has cooled down to 84°, 86° F. in winter, 
and 76°, 78° F. in summer, instead of putting in salt, sugar, and flour, 
and letting it self -ferment, it is stored or set away, with, in winter, 
about 1J gallons old barm, or Virgin; in summer, about 1 gallon ; and 
the tub is best kept uncovered during and after fermentation, where 
the temperature is between 60° F. and 70° F. In this case active 
fermentation is about over in 16 to 24 hours, when it is better to 
remove the tub to a cooler place. With this barm, as with Virgin, 
and every other yeast, it is not advisable to use it in sponge immediately 
or shortly after it has dropped. They should be left undisturbed for 18 
to 24 hours in a cool place, so that the old cells, which have then passed 
the active budding stage, may in peace and quietness resolve their 
protoplasm into spores or young cells. This is best promoted at a 
temperature between 40° F. and 60° F. That is the meaning of the 
advice to remove barm, after active fermentation, to a cool place. 
Barm at this stage should be kept in shallow tubs, or coolers, where a 
large surface is exposed to free oxygen. Free oxygen is indispensable 
to healthy cell life at this spore-forming stage." 

303. Flour Barms, " Glasgow Baker's" Formula.— "I 

purpose showing in this article that Scotch bakers can and do make 
healthy barm, and keep it so, without the slightest scientific knowledge, 
being solely guided by sight and taste. The grounds for the statement 
I shall fully advance after giving the recipe. 

304. " Ingredients. — 15 lbs. malt crushed, 4 lbs. English hops, 3 
qrs. home winter wheat flour, 1 qr. hard spring wheat flour (either 
Baltic or American). 

305. " Mode. — Boil hops with 3 gallons water for 15 minutes, with 
this liquor mash the malt • temperature, 165° F. (74° C.) ; allow it to 



204: CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

be in a tub for 4 hours, then wring or squeeze the malt by hand, keep- 
ing in mind that the last drops are the most valuable. Strain through 
a sieve of 6 holes to the inch, add 2 gallons hot water. The liquor 
should now be about 130° F. (53° C), which is the proper heat for the 
batter. This is made by adding flour, and doughing up the liquor to 
the consistency of a dough for morning rolls, as made in Scotland, or 
Vienna rolls in England. Your tub, containing the batter, should be 24 
inches wide, by 27 deep. It must now be drawn close to boiler for you 
to draw your water, which should be 220°. [As 212° F. is the boiling 
point of water, it is difficult to understand how " Glasgow Baker's " 
water, when drawn into the tub, should be at a temperature of 220° F.] 
For stirring, use a stick of hard wood, 1J in. in diameter, 4 J ft. long. 
Two men should be standing by, as stirring must be performed at such 
a speed that the strongest man cannot continue stirring more than 3 
gallons without a rest. The operation should be continuous, each man 
taking the stick alternately as the other rests. The most trying stirring 
is when the third 3 gallons have been added, because here the scald 
must take place. If you are to have a perfect scald 50 to 60 seconds 
will suffice. The stirring speed should be 120 to 130 strokes per minute. 
You will now know whether your water has been perfectly boiling, as 
the scald will be so thick after 45 seconds stirring that the strongest 
man will have difficulty in driving the stirring-pole through it. The 
mixture has now lost the appearance of raw flour and water, and 
assumed a rich yellow hue, and has the sweet taste of cooked flour. 
The critical stage has now been passed. Continuing the stirring at 70 
to 80 strokes to the minute, you add, in two equal portions, 6 gallons 
more water, stirring about 70 seconds for each of the 3 gallons. Your 
scald is now made, and should be put in a cellar with a fair ventilation, 
and at a temperature of not less than 60° in winter, and the nearer this 
temperature is kept to in summer the less difficulty will arise in keeping 
the barm sweet and regular. After standing 4 hours, several rents will 
appear across the surface, and little patches of white froth will rise from 
these rents. These will continue to grow larger for the next 18 hours. 
The scald may be stored from 24 to 36 hours old, provided the heat is 
not over 80°, for weather such as has been experienced in November, 
1884. The mode of storing barm is as follows: put this quantity of 
scald into a tub double the size of that used for scalding, add 3 gallons 
of healthy Parisian barm, and 14 lbs. fresh flour, stirring well, cleaning- 
sides of tub thoroughly. It will be up its full height in the tub in 
about 10 hours, and in from 18 to 24 hours time it will have dropped in 
the tub about 6 in. It should at this stage be divided into coolers — 
tubs 24 in. wide, 13 in. deep. Twelve hours after this it may be used 
for English or fancy bread, but for Scotch square batched bread it 
requires 48 hours in the coolers to mellow it sufficiently. New barm 
gives too much bulk, and cannot be skinned or piled, as the Scotch 
bakers term the texture of the loaf. Barm for storing should not be 
more than four days old — that is from the date of storing. 

" I have in the foregoing treated of the methods of producing healthy 
barm, and I now offer a few hints as to the signs by which practical 
men know whether barm is or is not healthy. When the barm comes 



MANUFACTURE AND STRENGTH OF YEASTS. 205 

up well in the tub, with thousands of little bells coming up to the sur- 
face, and breaking as they come, driving the large dull and floury bells 
to the sides of the tub, where they disappear slowly. When barm is 
ripe for cooling, clear bells, or, as bakers term them, " black bells," 
appear on the clear surface. They appear at first sight " black " on a 
white surface ; but, on looking into them, you see they are simply a 
transparent bubble without trace of flour. Barm makers have got to 
know, from a long course of observation, that these are the sure 
signs of perfect healthy barm, and they state they have never seen bad 
bread made from barm of this description. The term " Lifey " is 
applied to healthy barm ; the term " Dead " is applied to barm when all 
the active healthy little bubbles or cells cease to come up and explode 
on the surface. By the very face of it, when in this state, a practical 
man on looking at it will shake his head, and say, " It is gone ; I will 
not use it." He will then taste it, and if the taste bears him out, he 
will make up his mind to put it down the sink. This is the knowledge 
the practical man has, and his discoveries, it will be observed, are made 
through sight and taste only. 

" It will naturally be asked " Why don't you show us that your practi- 
cal man can keep his barm healthy, and how he does it 1 " This is how 
it is done. When he sees the bubbles rising feebly, he at once says 
there is a want of " life " or " forces," and will infuse fresh life by stor- 
ing half from a young barm 36 hours old, and half the 48 or 72 hours 
sickly barm. This will, under ordinary circumstances, bring it right, 
but if the appearance is still dull he will keep adding every time he 
stores a new scald, a larger proportion of the young barm, till he is 
satisfied he has brought it round. The only exception to such is when 
barm gets fired, through a thunderstorm, in which case, as a rule, it is 
completely killed, and cannot produce sweet bread. It often happens, 
however, in a cellar with, say, 10 tubs of barm, that only half or so are 
affected by the electric fluid, the remaining ones keeping quite "healthy." 
In such a case the baker can start fresh lots from the uninjured tubs, 
but if all are fired, then he must go and get a store of " healthy " barm 
from some neighbour who has been less unfortunate than himself ; but 
here again he must use his judgment as to whether his friend's barm is 
" healthy," and I have never known a practical man deceived in such. 
Many of the men who make the barm in the largest bread factories in 
Scotland, have no scientific knowledge of barm. They never read a 
book on the subject, nor have they ever heard the matter contained 
therein spoken of. Many of the barm makers in Scotland started as 
careful lads, entrusted with the scalding of the tubs with boiling water, 
which is most essential, in order to kill the particles of old fermentation; 
and I have known such lads who could neither read nor write become 
highly successful barm makers. 

" This article is not written to show that science is useless to bakers, 
but is a simple statement of facts, showing the stage of perfection at 
which practical men had arrived before scientists took the subject in 
hand. I have known such bakers who did not require to change their 
store for two years at a time, and have had successful runs of sweet 
barm for years." 



206 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

306. It is somewhat amusing to read the statement of the purpose 
for which this article was written — namely, to show how Scotch bakers 
make healthy barm, without scientific knowledge. There is an old 
story of a man who in advanced years discovered, with much surprise, 
that he had been talking prose all his life without knowing it. Scotch 
bakers have reduced barm and bread-making to a science, " without 
knowing it." Defining science as knowledge, systematically arranged — 
;such knowledge to be true science must be founded on careful and 
patient observation. Notice how thoroughly scientific the " Glasgow 
Baker's " method is. He works with exactness ; at every stage of his 
process he brings to bear the result of life-long observation ; as a conse- 
quence, he is able to tell directly whether the growth of his barm is good 
or bad : all this is the application of genuine scientific methods. But 
the "Glasgow Baker's" science is, although true science, defective and 
imperfect science. The methods of how to work have been conquered ; 
but the reasons why have been ignored. Science insists, not merely 
that methods shall be systematic, accurate, and good, but also insists on 
knowing why they are so. The man who knows the why and wherefore 
-of a step has some chance of improving on the methods he has been in 
the habit of using ; the man who only knows it is so, " because it is so," 
simply flounders hopelessly, at once getting out of his depth, if he ven- 
tures in the unknown waters of attempted improvements. For their 
own sakes it is time that practical men gave up that idea of science 
being a sort of fetish, having no connection with practical men's work 
or ways. Science has its practical side, and is in that respect identical 
with the ways and methods of practical men : the fact that it also 
demands an examination into the why and wherefore of things should 
simply be an additional commendation to men of practice, for nine-tenths 
of the discoveries and improvements made in arts and manufactures 
have resulted from careful inquiry into the connection between cause 
and effect. 

307. Suggested Modifications of Flour Barm Recipes. 

— The both of these recipes are the work of practical men who are 
capable of making, and do make, some of the best bread in the world : 
the methods used are therefore justified by their being successful. 
There is however one point in which, in the author's opinion, the 
methods might be modified with advantage. It will be noticed that in 
both cases the malt is first mashed with water, so as to convert its starch 
into maltose and dextrin. In the next place this wort is mixed with 
flour, so as to make a batter, which in its turn is scalded (that is, the 
starch of the flour is gelatinised), by the addition of hot water. Now, 
in this case the hot water is added to the batter containing the malt 
wort ; the inevitable consequence of the addition of boiling water to 
this must be to destroy some of the diastase of the malt, and conse- 
quently to lessen the action which it afterward exerts on the gelatinised 
starch of the flour. Notice how particularly it is directed that the mix- 
ture shall be stirred sharply : this must be done so rapidly, that it is 
recommended that two men be ready, the one to relieve the other. The 
rapid stirring, by quickly cooling the added water, by its intermixture 
with the remainder, lessens the danger of altogether destroying the 



MANUFACTURE AND STRENGTH OF YEASTS. 207 

diastase. As an alternative method, it is suggested that the flour should 
be mixed with warm water and then scalded in a separate vessel ; then 
when the scalded flour had been cooled to a temperature of from 65° to 
70° C, the malt wort might be added. Diastasis would then proceed 
all the more vigorously, as the malt wort would not have been in any 
way injured by the addition to it of boiling water. The risk of spoiling 
the whole of the barm, during scalding, would in this way be almost, if 
not entirely, avoided. 

308. Microscopic Character. — Viewed under the microscope, 
Scotch flour barms always show a certain proportion of lactic ferments 
as a normal constituent. Thorns argues that their presence is bene- 
ficial, and states, in favour of that view, that when he has taken steps 
for brewing barm in which lactic ferments are absent, that the bread is 
of inferior quality. The probable function of lactic ferments during 
panification will be dealt with in a future chapter. Scotch bread has 
always a slight acid flavour, totally distinct from what is understood in 
England as " sourness " of bread, but more resembling in type the 
flavour of buttermilk. Germans immediately notice this characteristic 
of Scotch bread. It should be explained that this peculiarity is not 
quoted as a fault : in fact, those accustomed to bread of this flavour 
find something lacking if the acidity be absent. 

309. Strength of Various Yeasts. — There follow particulars 

of the strength of various samples of yeasts, when tested in the yeast 
apparatus. The first series have been made with yeast mixture, and 
water at 30° C. : in those of the second, sugar and water at 25° C. were 
adopted. A quarter ounce of compressed brewers' yeasts were taken 
for each test, and six ounces of the patent yeasts, water then being dis- 
pensed with. The same brand is throughout represented by the same 
letter ; thus giving an opportunity of comparing one and the same yeast 
over a considerable time. 

310. First Series. 

No. 1. Compressed Yeast, A, 27th April, 1885. 

No. 2. Brewers' Yeast, A, from London yeast merchant, 1st May, 

1885. 
No. 3. Compressed Yeast, B. 5th May, 1885. 
No. 4. Dublin Patent Barm, 6th May, 1885. 
No. 5. Ditto, another sample, 6th May, 1885. 
No. 6. Brewers' Yeast, A, 7th May, 1885. 



208 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



Time. 



o 




I 


hour... 


2 


hours 


3 


,, ... 


4 


,, ... 


5 


i» 


6 


>» ••• 



Gas Evolved in Cubic Inches. 



No. i. 



cvo 
217 



6 3 o 

I 34 
130*3 1 

I 24 ' 
i54'5< 

I 15 ' 
170-2-' 



No. 2. 



OO 



2 '3 < 



-33'2 



35*5 



}.8 7 

hi'7 
65-9 J 



No. 3. 




No. 4. 




No. s. 



o-o 
o-8 
4'5 

'5 
2 

3i*f 



fio- 



43*2 J 



No. 5. 



O'O 



4-3 

16-5 
35 'o 
53 -o 
75 -o 
98-5 



H 



I2'2 



18-5 
18-0 



22*0 



23*5 



No. 7. Compressed Yeast, A, 7 th May, 1885. 

No. 8. Brewers' Yeast, A, 14th May, 1885. 

No. 9. Dublin Patent Barm, another sample, 14th May, 1885. 

No. 10. „ 4th sample, „ 

No. 11. Dutch Pressed Yeast, from Dublin, 21st May, 1885. 

No. 12. French „ „ ,, 



Time. 



O 

1 hour 

2 hours 

3 „ 

4 „ 

5 » 

6 „ 



Gas Evolved in Cubic Inches. 



No. 7. 



o*o 



24*5 
60 '9 



104-0 



24*5 



J36-4 

I 32-0 

U2.5 
I58-5 

H7'5 
175-0-' 



No. 




No. 9. 



0'0-> 

hi-2 
n-6 

h3'9 
35'5i 

Y34-2 
697 { 

}3o-8 



1 00 -5 
144-8 = 
178-0- 



44 '3 
33*2 



No. 10. No. 11. 





No. 



0*0 
35"0 

86-3 
132-0 
162-3 

178-5 
178-6 



}„* 

} 5 ,3 

457 
30*3 

l6'2 



No. 13. Brewers' Yeast, A, 29th May, 1885. 

No. 14. Patent Barm, from near Dublin, 29th May, 1885. 

No. 15. Brewers' Yeast, A, 11th June, 1885. 

No. 16. Brewers' Yeast, A, 25th June, 1885. 

No. 17. Compressed Yeast, A, 25th June, 1885. 



MANUFACTURE AND STRENGTH OF YEASTS. 



209 



Time. 



O 

1 hour 

2 hours 

3 » 

4 » 

5 ,. 

6 ,, 



Gas Evolved in Cubic Inches. 



No. 13. 



O'O 

2-4 

13-9 

29-0 

44*5 
6 



J 2-4 

} I5 -5 

Ki7*3 

i-8 

}i8-5 



80-3 



No. 14. 



O'O 
2'0 
9-0 

9'3 
3i'3 

44 
58-3 



j- 2'0 

I 7-0 

ho'3 
I9'3 i 

[l2'0 
I "? 

j-127 

1 14-3 



No. 15. 



3 '4 



3 '4 



^1 
M3'9 

I7 ' 3 * 
M.67 

34*o < 

U6-o 

50-0^ 

M9*5 

69 ' S I « 
85.5 J 



No. 16. 



1 -6 { 

} 8-4 

M7"o 

2-C ^ 



IO'O 



25'5 

U6-o 
■c J 



58-5 



74' 



}i6-3 



No. 17. 



37-8 

h47'2 
85'o{ 

f39'3 
124-3 i 

h36'3 
i6o*6< 

h 6-9 

167-5 { 

j- o-o 

167-5 } 



It will be observed that the pressed yeasts keep pretty uniform with 
regard to gas evolved. The samples of the same merchant's brewers' yeast 
vary rather more, while the patent barms exhibit wide ranges of difference. 

It must not be forgotten in comparing these results that a quarter- 
ounce of the brewers' and pressed yeasts are employed for each test, 
while 6 ounces of the patent yeasts are taken. Thus, 6 ounces of No. 10 
produce 44/5 cubic inches of gas, while J ounce of No. 11 produces 
171'8 cubic inches. "With fermentation proceeding under exactly the 
same conditions, about ninety times as much by weight of No. 10 would 
be required as of No. 11 to produce the same amount of gas. 

311. Second Series. 

No. 1. Compressed Yeast, A, 2nd July, 1885. 
No. 2. Compressed Yeast, B, „ 

No. 3. Compressed Yeast, B, 8th July, 1885. 
No. 4. Compressed Yeast, A, 14th July, 1885. 
No. 5. Compressed Yeast, B, 15th July, 1885. 
No. 6. Compressed Yeast, A, ,, 



Time. 


Gas Evolved in Cubic Inches. 


No. 1. 


No. 2. 


No. 3. 


No. 4. 


No. 5. 


No. 6. 


t 

1 hour ... 

2 hours... 

3 » ». 

4 »» ••• 

5 » •• 

6 „ ... 


O'O. 

} 7'o 
7'o< 

f-12'0 
I9-0 \ 

32 -o{ 

[13-0 

45 -ol 

58-i { 
M4'i 

72-2 J 


O'O-. 

1 77 

}i7-3 
25 'o< 

1 187 
437 < 

eJ 17 ' 5 

}i7-8 
79 'Ol 

M9'0 
98 -o J 


OTK 

[ 6-6 
6-6 J 

}i7-9 
24-5 < 

M7'o 
41 *5 i 

|i7-5 
59-o < 

U6-o 

U8-5 
93 5 J 


o-o-, 

3'i \ 

\ 9'9 
i3'o< 
}n-5 

24-5 i 

36-3 { 

49'2 < 

\i3'3 
62-5 J 


OTK 

| 5-o 

\i6-6 
21 -o< 

\ 22 7 
437< 

>47'5 
93-2' 


0'0, 

} 5-o 

Vl2'0 
I7'0 J 

[iH-8 
35-8^ 

>45"9 
817^ 



210 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



No. 7. Patent Yeast, Brighton, 15th July, 1885. 

No. 8. Compressed Yeast, B, 24th July, 1885. 

No. 9. Compressed Yeast, A, ,, 

No. 10. Brewers' Yeast, B, 

No. 11. Brewers' Yeast, C, ,, 

No. 12. Scotch Flour Barm, „ 



Time. 

O 

1 hour 

2 hours 

3 » ••• 

4 » ••• 

5 „ - 

6 „ ... 

7 ,. ••• 

8 „... 

9 „ ■■■ 



Gas Evolved in Cubic Inches. 



No. 7. 



o-o 
o 
7 

6'2 



}4'5 



13-4 



19-6- 



No. 8 




No. 10. 




No. 11 



NO. 12. 




No. 13. Patent Yeast, Brighton, 24th July, 1885. 

No. 14. Compressed Yeast, B, 29th September, 1885. 

No. 15. Compressed Yeast, C, „ 

No. 16. Compressed Yeast, A, „ 

No. 17. Compressed Yeast, B, 7th October, 1885. 

No. 18. Compressed Yeast, A, ,, 



MANUFACTURE AND STRENGTH OP YEASTS. 



211 



Time. 



... . 

1 hour . 

2 hours 
3 

4 



5 , 

6 , 

7 , 

8 , 

9 , 



Gas Evolved in Cubic Inches. 



No. 13. 



No. 



} i-3 } 6' 

i-3 6-o 

} 3-4 \iS' 

47 i 2i - M 

/ 5 ' 3 



7 

IO'O 

157 



57 



27-3 i 

} 5-2 



}.5- 
37-o { 



No. 15. 



No. 16. 



o-o . 

5-0 

i9'3 < 

35*3 { 
M3* 
50-2 < 487 < 

M5'3 M4* 

65'5 6 3 '5 

M27 [l2'0 

75'5 J 



78-2 



3-4 \ 

I.V2< 

U2-8 
•o 
V io* 

}l2- 

}n-o 



3 
26-0 
36 
49-0 

60 



No. 



O'O. 

} 4 ' 5 

4-5 

M5'2 
'97 

M5-3 
•o 

}i3*4 

} 9*4 
72-8 ] 

^ 77 
80-5 } 



35 -o 
50*0 

63-4 



No. 18. 



38'3 



57*3 



74'o 



107 
10*4 



167 



No. 19. Compressed Yeast, D 3 7th October, 1885. 

No. 20. Compressed Yeast, B, 8th October, 1885. 

No. 21. Compressed Yeast, B, soaked in water at 25° C. one hour 

before testing, 8th October, 1885. 

No. 22. Compressed Yeast, B, 12th October, 1885. 

3STo. 23. Compressed Yeast, B, 14th October, 1885. 

No. 24. Compressed Yeast, A, ,, „ 



Time. 




Gas Evolved in Cubic Inches. 



No. 20. 



O'O 

4"2 
15-0 
28-0 
40*5 
53*5 
65-0 

77*5 

907 
[03-2 
[14-6 



4'2 
n-8 
13-0 
12-5 
13*0 
115 

I2'5 

13-2 
12-5 
1 1 -4 



No. 21. 



O'O 



4'6 
4*6 < 
J-127 

M4'2 
1*5 

M37 

' 2 \ 
\i2-2> 

*°1 

85'5] 

M4o 
99'5i 

II3 ' 5 1 o 
I io-8 



7*3 
3i*5 
45'2 
59*2 
72*0 = 



124-3 



No. 22. 



o-o 

5*5 
21-5 



5'5 
16 -o 



.14-5 

36-0^ 

}i5-2 
5i*2< 

U 5 -8 
67 -o\ 



81 -o 



No. 23. 




No. 24. 



YO J 



212 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



No. 25. Compressed Yeast, E, 14th October, 1885. 
No. 26. Compressed Yeast, F, „ „ 

No. 27. Compressed Yeast, A, 19th October, 1885. 
No. 28. Compressed Yeast, B, ,, „ 

No. 29. Compressed Yeast, A, 20th October, 1885. 
No. 30. Compressed Yeast, B, ,, ,, 



Time. 


Gas Evolved in Cubic Inches. 


No. 25. 


No. 26. 


No. 27. 


No. 28. 


No. 29. 


No. 30. 




1 hour 

2 hours 

3 » 

4 ,i 

5 » 

6 „ 


O'O s 

[ 2'2 
2-2 

7-5 
97 

2-s 

12*2 - 

^3-3 

25'5 

9-0 

34'5 

7'5 
42-0 J 


O'O. 

} i-8 
r-8{ 

I 5 ' 2 
\ 6-o 

iyo\ 

7'° 

20 '0 \ 

8-o 
2 8-o 

£ 6*o 

34*0 ) 


O'O, 

} 37 
37 { 

\ 7-6 

1- 9'9 

2I'2 ; 


O'O, 

\ 8-2 

8-2 { 

H3'3 
2i*5i 

KI3-8 

35 '3 j 


O'O 

[ 2'0 
2-0 

4-2 

6'2 

7'8 
14-0 

8-5 

22'5 

9'0 
3i-5 

7'5 
39-0 } 


O'O-, 

} 5'2 

5-2 

\ 14-3 

i9"5i 
35*5 ^ 

5i-o^ 

J 4'5 
65-5 

13-2: 

787 j 



This series of tests affords an opportunity of comparing the one yeast 
over a considerable period of time On being subjected to such a test,, 
some yeasts are found to behave very regularly, whilst others fluctuate' 
considerably. All yeasts hitherto examined evolve more gas in summer' 
than in winter. This does not depend on the fermentation being con- 
ducted at a higher temperature, because, in the yeast testing apparatus^, 
the fermentation is maintained throughout at a constant temperature. 
In order to show the effect of warming yeast before its use, Nos. 20 and 
21 were tested on the same day ■ the only difference was that the latter 
sample was allowed to stand, mixed with water at a temperature of 
25° C, for an hour before being tested. The results show that about 
ten per cent, more gas is evolved by the warmed yeast. 

When the readings are not given for any particular yeast to the full 
extent of the column, it does not mean that the yeast ceased to evolve 
gas at the time of the last reading given, but that the taking of read- 
ings was not continued further. 

The conditions under which the Scotch Flour Barm was examined 
were scarcely fair to it, as it was three or four days old when it arrived 
here, and had travelled at the very hottest part of the summer.. 



MOULDS AND FUNGOID GROWTHS. 313 



CHAPTER XIII. 

MOULDS AND FUNGOID GROWTHS. 

312. The nature of these has been already referred to in chapter 
IX., and the mould of beer, mycoderma vini, described and its nature 
explained. The moulds are all of them members of the fungus family. 
A few other varieties, because of their having more or less connection 
with the subject of this work, require description. 

313. Mycoderma Aceti. — This organism effects the change of 
wine and beer into vinegar. The reaction is one of oxidation of the 
alcohol present : in the first place, aldehyde is formed, and then this body 
is oxidised into acetic acid, according to the following equations : — 



2C 2 H 5 HO + 

Alcohol. 


n° 2 

Oxygen 


= 


2C 2 H 4 + 2H 2 

Aldehyde. Water. 


2C 2 H 4 

Aldehyde. 


+ ° 2 

Oxygen. 


- 2HC 2 H 3 2 

Acetic Acid. 



The acetification of wine or beer, under normal circumstances, is un- 
doubtedly due to the action of this m.ycoderm, for no acetic acid is 
formed on exposing dilute alcohol to air alone ; but considerable doubt 
exists as to the exact function of the organism, which " apparently ex- 
ercises an influence similar to that of finely divided platinum, and quite 
different from that of yeast and other microscopic organisms, which 
•excite fermentation " (Miller's Elements of Chemistry.) 

Mycoderma aceti forms a mycelium on the surface of liquids, possess- 
ing a certain amount of tenacity : viewed under the microscope, this 
mycelium is seen to consist of chains of minute cells varying from 1 to 5 
mkms. in diameter. The exact botanical position of these organisms is 
very indefinite, but the balance of evidence is in favour of classing them 
among the bacteria. 



'» 



0o ^Q^^ 00 OooO° 00 




Ocpooqo 
fig. 35. — Bacterium Aceti (after Kopf). 

Most antiseptics, and especially sulphur dioxide, are inimical to ace- 
tous fermentation. Mycoderma aceti is often termed " mother of vine- 
gar." Patent yeasts, on developing a film of either mycoderma vini or 
aceti, are often said to have become " mothery." 

314. Penicillium GrlaUCUm. — This is the ordinary green mould 
of bread, jam, &c. The base of this consists of a mycelium bearing both 



214 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

submerged and aerial hyphse. The upper ends of the aerial hyphse 
terminate in a string of conidia or spores, which break off on the slightest 
touch ; these constitute the green powder which gives this mould its 
characteristic appearance. One of these spores, on being sown in an 
appropriate medium, as hay infusion or Pasteur's fluid, germinates and 
produces a young penicillium. The conidia retain their vitality for a 
long time, and from their extreme minuteness are readily carried about 
by the air ; hence substances that offer a suitable medium for the growth 
and development of moulds, become impregnated on being exposed to 
the atmosphere. 

Under favourable circumstances, penicillium developes with extreme 
rapidity ; some few years since the barrack bread at Paris was attacked 
by this fungus, a few hours was sufficient for its development, and the 
mould was in active growth almost before the bread was cold. It is 
stated that the spores of this species are capable of withstanding the 
heat of boiling water, so that the act of baking an infested flour would 
not necessarily destroy the spores. 

315. Aspergillus GlauCUS. — This is another mould very similar 
to penicillium in appearance and colour, but having at the ends of its 
hyphse small globose bodies containing the spores ; these bodies being 
termed sporangia. 

316. MllCOr Mucedo. — This mould develops well on the surface 
of fresh horse dung ; this substance, if kept warm, will be found after 
two or three days covered with white filaments, these being the hyph£e y 
and termining in rounded heads or sporangia. In form M. mucedo 
somewhat resembles A. glaucus, but is distinguished from it by having 
a whitish aspect, A. glaucus being of a greenish colour. 

317. MicrOCOCCUS ProdigiOSUS. — This organism consists of 
round or oval cells, from 0*1 to 1 mkm. diameter. These are at first 

.. i *% 







^3 



fig. 36. — micrococcus prodigiosus, Cohn, x i2co (from nature). 

colourless, but gradually assume a blood-red tint : they grow on wheat- 
bread, starch paste, &c. M. prodigiosus is the cause of the appearance 
known as blood-rain occasionally seen on bread : at times the growths 
proceed so far as to produce dripping blood-reel patches on the bread. 

The author had recently a sample of bread sent him for examination 
which contained small red spots, at first sight very like those produced 
by this organism. Microscopic examination revealed that they were 
produced by the accidental enclosure within the bread of filaments of red 
wool : these had in some way got into the dough, and had been baked 
with the bread. 



MOULDS AND FUNGOID GROWTHS. 215 

318. Musty and Mouldy Bread. — Mouldiness may be very 
often noticed in bread which has been kept for a few days : at times, a 
loaf of one day's production will remain quite sound, while another will 
rapidly become mouldy. The "Analyst" of October, 1885, contains an 
article by Percy Smith, giving an account of some experiments made by 
him on musty bread. The bread when new had no disagreeable taste, 
but on the second day had become uneatable. Smith made a series of 
experiments, among which were the following : — 

(a) Musty bread, one day old, soaked in water, enclosed between 

watch glasses. 

(b) Flour from which the bread was made, similarly treated. 

In six days a had begun to turn yellow, emitted a disagreeable odour, 
and began to assume a moist cheesy consistency and appearance. This 
portion was found to be swarming with bacteria. On b, mucor mucedo 
grew in abundance, the flour ultimately dried up without further 
change. 

(c) Sweet bread similarly treated. 

Aspergillus glaucus appears, but no mucor, neither does the bread 
become cheesy nor evolve odour of musty bread. The following are 
Smith's conclusions based on these and other experiments. 

" Ordinary bread turns mouldy owing to the growth of A. glaucus. 
Musty bread, on the other hand, yields both A. glaucus and M. mucedo, 
and then undergoes putrefactive decomposition, becoming the home of 
vibriones and bacteria. These organisms, of course, can have nothing to 
do with the mustiness, they only flourish because there is a suitable 
nidus for their growth. It is, however, curious that the musty bread 
should decay while the sweet bread should not, whilst the only apparent 
difference between them is in the growth of M. mucedo. The suspected 
flour produces an abundant crop of mucor, but does not decay. This is 
no doubt due to the fact that starch is not so suitable a nidus as is 
dextrin for bacteria. Perfectly pure flour failed to decompose when 
kept between watch glasses, but when placed in a damp cellar readily 
became musty, and produced a crop of M. mucedo." He further con- 
cludes that this fungus is the cause of the mustiness in the cases cited, 
although other species may possess similar properties. Smith is of 
opinion that of the musty bread and flour supplied to him the following 
is the history : — "The flour was stored in a damp place, causing fungoid 
growth: to avert decomposition, the flour was then baked." (This idea 
occurred through the flour having a dark colour, as though charred). 
When the bread was baked the assimilation of moisture regenerated 
the fungus, thus causing the bread to become musty, for which result it 
is not necessary for the plant to arrive at maturity ; the disagreeable 
taste being developed as soon as flocci are visible under the microscope. 
Mucor has apparently a specific chemical action on bread that is not 
possessed by Aspergillus glaucus. 

The baking of the flour seems rather a peculiar treatment, since any 
baking that would produce anything like charring in the flour would 
entirely destroy its gluten and consequent doughing properties. 

319 Diseases Of Cereals. — Certain diseases to which the cereal 
plants are subject are due to parasitic fungoid growths. Among these 



216 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



are mildew, smut, bunt, and ergot, 
sidered at this stage of our work. 



There nature may briefly be con- 



320. Mildew. — To the farmer, this blight is unhappily too familiar ; 
if a wheat field be examined in May or June a greater or less number 
of the plants will appear as though some of the lower leaves had become 
rusty, at the same time the leaves are sickly and atrophied. As the 
disease develops the number of rusty leaves increases ; the " rust " itself 
will be found on examination to consist of the spores of a fungus, known 
as the Puccinia graminis or corn mildew. The mycelium penetrates the 
tissues of the leaves, occupying the intercellular spaces, and thus 
gradually destroys them, with the effect of seriously injuring and reducing 
the corn crop. 

32 1 . Smut. — This disease is also known as " dust brand," " chimney 
sweeper," and by other names all referring to the black appearance of 
ears of grain infested by it. When the grain is nearly ripe, there will 
be noticed here and there in a wheat field shrivelled looking ears, which 
look as though covered with soot. Smut is due to a fungus which has 
received the name of Ustilago segetum. The fungus develops within the 
seeds, destroying the contents of the grain, and replacing them by a 
mass of spores which appear as a fine brownish black powder. Smut is 
a very destructive parasite, and attacks barley, oats, and rye, and also, 
although to a somewhat lesser extent, wheat. Viewed microscopically, 
the spores of U. segetum are found to be spherical, and to have a diameter 
of about 8 mkms. ; their appearance is shown in the following figure : 




fig. 37. 

a, Smut, b, Bunt x 400 diameters. 



MOULDS AND FUNGOID GROWTHS. 217 

322. Brefeld on Identity of Smut and Yeast. — Grove, in 

his exceedingly useful work on " Bacteria and Yeast Fungi," quotes at 
length some recently advanced views of Oscar Brefeld, the German 
naturalist. Grove at the outset discounts Bref eld's opinions by recording 
that his (Brefeld's) previous researches have often been conducted in an 
extremely careless manner. Brefeld points out that the successive 
generations of smut conidia resemble saccharomyces, and claims that 
they are identical with them. He found on cultivating smut spores in 
suitable media that they continued to bud until the whole of the nutri- 
ment was exhausted ; on these buds being again sown in a fresh quantity 
of the medium, budding again commenced. This process was repeated 
some thirty times in a period of about a year — throughout, the budding 
conidia resembled yeast in form and dimensions. But little is said as 
to whether these budding spores of ustilaginece possess the power of 
exciting alcoholic fermentation. 

Not only Brefeld's opinions, but also those of other modern observers, 
seem gradually to be inclining to the view that yeast is not absolutely 
a separate and distinct organism ; but that it consists of the conidia, 
or spores, of higher fungi in a budding condition. But until a satisfactory 
theory is enunciated, in which the connexion between yeast and other 
species is clearly demonstrated, it is for the present far better to treat 
the saccharomycetes as a separate and distinct order of fungi. 

Nevertheless, this view of Brefeld's is of considerable interest to the 
student of panary fermentation. In the fermentation of must, the yeast 
spores are carried on the skin of the grape, being associated with the 
fruit during the time of its growth. In event of Brefeld's hypothesis 
being correct, then the yeast of bread fermentation would have its 
ancestor in an organism also accompanying the grain during the growth 
and development. In leaven, and also flour barms, fermentation sets 
in not only without any apparent contact with yeast, but also frequently 
under conditions in which it is extremely difficult to see from whence 
yeast organisms could have found their way into the fermenting medium. 
The early history of leaven is lost in obscurity, and no means exist of 
ascertaining whether bread was originally leavened from a yeast of 
alcoholic fermentation. But, if the conidia of Ustilago be identical 
with yeast, the latter being simply the same organism, functioning 
under different conditions, then the origin of the saccharomyces of so- 
called spontaneous bread fermentation is traced at anyrate to a parasitic 
fungus normally associated with the wheat grain. To the bread-making 
student Brefeld's theory is an alluring one ; but it must be remembered 
that as yet the evidence in its favour is far from sufficient to establish 
its right to general acceptance. 

323. Bunt Or Stinking Rust. — Unlike smut, bunt produces no 
external signs of its presence in a wheat field : there is no sooty appear- 
ance of the ear, nor any rust about the leaves. It is not until the 
wheat is threshed from the straw that the bunted grains are discovered 
in the sample. Externally, these grains are plumper than those w r hich 
are sound ; but on their being broken, the interior, instead of being 
white and flour-like, is found to be filled with a black powder, having a 
greasy feel when rubbed between the fingers, and a most foetid and 



218 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

unpleasant odour. This dust consists of the spores of a fungus termed 
Tilletea caries, mixed with portions of its mycelium. The spores are 
much larger than those of smut, and viewed under the microscope 
appear as shown in Fig. 37 : they are about 17 mkms. in diameter. 

The presence of bunt is said not to affect the wholesomeness of flour ; 
it is stated that bunted flour is at times made up into gingerbread ; the 
other condiments used masking its colour and odour. With the ex- 
treme care manifested in modern systems of milling, it is improbable 
that bunt often finds its way into the flour. 

324. Ergot. — This disease is almost exclusively confined to rye ; 
like bunt and smut, ergot is due to a fungus which develops within the 
grain, filling its interior with a compact mass of mycelium and spores, 
and altering the starch cells by replacing the amylose with a peculiar 
oily matter. This fungus is termed Oidium abortifaciens. The ergo- 
tised grains are violet-brown or black in colour, moderately brittle ; and 
when in quantity evolve a peculiar nauseous fishy odour, due to the pre- 
sence of trimethylamine. Ergot possesses powerful medicinal effects, and 
when taken in anything over medicinal doses, acts as a violent poison. 
The presence of ergot in flour is therefore extremely dangerous. 

Chemical tests for the detection of ergot and moulds will be given in 
the analytic section of this work. 






PHYSICAL STRUCTURE OF THE WHEAT GRAIN. 



219 



CHAPTER XIV. 

PHYSICAL STRUCTURE OF THE WHEAT GRAIN. 

325. The wheat grain is that part of the plant on which falls the 
task of performing the functions of reproduction, hence all its parts are 
specially fitted for that purpose. The germ, or embryo, of wheat is 
that portion of the seed which ultimately develops into the future plant. 
The main body of the grain, composed principally of starchy matter, is 
termed the " endosperm : " its function is to supply the germ with food 
during the first stages of its growth. Besides these there are the vari- 
ous outer and other coverings, destined for the adequate protection of 
the seed, which together constitute the bran. The physical structure of 
the wheat grain requires for its systematic study the use of the micro- 
scope : the descriptions following therefore include practical directions 
for microscopic observation. The arrangement adopted is that most 
easily followed by the student in a course of actual microscopic work. 
For earlier studies it is well to obtain from the dealer ready-mounted 
longitudinal and vertical sections of a grain of wheat. In every case, 
practise sketching what is seen : as before stated, the accompanying 
figures are facsimiles of those which the student should himself make. 

326. Longitudinal Section of Whole Grain.— In the first 

place, examine the longitudinal section of the grain of wheat with the 
3in. objective ; the whole of the grain will then be in the field. Try, 
in the next place, to make a sketch of it. For this purpose the student 
should use a camera lucida if he should possess one. Trace in the out- 
line and other principal lines with a hard pencil ; then go over them 
with a lithographic pen and liquid Indian ink. It will be impossible to 
get in all the details, the effort should be rather to show what is 
essential ; thus the object of the sketch with the low objective is to get 
an idea of the general shape and arrangement of the different con- 
stituent parts of the grain. When the drawing is complete, mark 
underneath the number of diameters to which it has been magnified. 




fig. 38.— longitudinal section of grain of whfat, magnified eleven 

diameters. 



220 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

This particular section is not made exactly through the crease, but 
while starting pretty well from the middle of one end, has inclined to- 
ward the side while being cut. The germ is seen at the right hand end 
of the figure, and a fair idea of its size, compared with that of the endo- 
sperm, which constitutes the remainder of the grain, may be obtained. 
Enclosing both germ and endosperm is the bran. With this low power, 
the square cells of the bran, lining the interior, and known as cerealin 
cells, are just visible. The name commonly given to these is, by the 
bye, a misnomer, they are not "gluten" cells, for the reason that they 
contain no gluten. In cutting the section, the outer skins of the bran 
have become separated from the inner, and so increase the apparent 
thickness of the skin. The more minute examination of the grain is 
best made by the aid of the higher powers. 

327. Transverse Section of Wheat Grain.— Examine next 

a transverse section of a grain of wheat ; the section, below figured, 
Figure 39, was cut from a grain of Kubanka wheat, and passes through 
the germ. 




FIG. 39. — transverse section of grain of wheat, magnified 13 diameters. 

On examining carefully such a section as that shown, the pigment- 
containing cells are seen in a line passing completely round the grain, 
and forming a thick spot of colour in the crease. Notice that the cere- 
alin cells of the bran do not continue round the germ. Observe also as 
much as possible of the structure of the germ itself, and the relative 
dimensions and positions of germ and endosperm. 

Examine the same section in the next place with the 1-inch objective. 
The outer skins of the bran are here seen more plainly ; the square 
cerealin cells are also plainly visible. Notice that near the bottom of 
the crease, the cells, instead of being in single line, are in double, be- 
coming more numerous and irregularly arranged as the bottom is ap- 
proached. The crease distinctly bifurcates at the bottom; the pigment 
layer of the grain becomes considerably enlarged, and its section is seen 
at the middle of the fork as a dark yellow spot of considerable size. 
With this power the starch granules also become visible. 



PHYSICAL STRUCTURE OF THE WHEAT GRAIN. 



221 




FIG. 40. 



-view of crease in grain of wheat, as shown in a transverse 
section, magnified 110 diameters. 



328. Section Cutting and Mounting. — It has been assumed 

that, for the purposes of making these studies and sketches, the student 
has had in his possession sections that he has purchased ready mounted. 
He will probably at this stage of his work wish to prepare and mount 
sections of his own. Wheat in its ordinary state is too brittle to per- 
mit of its being cut in thin sections. In the first place, therefore, soak 
a few grains in water for about twenty-four hours ; the water may be 
luke-warm, say at a temperature of 80° to 90° F. When the grains, 
have become moderately soft, sections may be cut from one of them. 
For this purpose a very sharp razor, which has been ground flat on one 
side, is generally used. Take one of the grains between the thumb and 
linger, cut off one end, and then proceed to slice off sections as thin as 
possible. Some little practice will be necessary before they can be suc- 
cessfully cut of the requisite thinness. 

This operation is rendered easier by the use of a section cutting table. 
This little piece of apparatus consists of a plate of brass, the surface of 
which has been turned perfectly plane, in the centre is fixed a tube con- 
taining a piston, which may be raised by means of a screw. The object 
whose section it is wished to procure is first cast into a block of either 
cocoa butter or solid paraffin. In either case the temperature of these 
must only just be raised to the melting point. This block of solid 
paraffin or other substance is next trimmed down so as to go into the 
tube of the section cutting table. Adjust the screw at the bottom so 
that the grain is in about the right position, then draw the razor across. 
the top of the tube and cut off the upper part of the grain ; screw up the 
piston at the bottom of the tube very slightly, and cut off a section by 
again drawing the razor across the plane surface of the table. In this 
manner thin sections may be cut with comparative ease. Having thus 



322 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



obtained the sections, wash them in a little spirits of wine and transfer 
to a slide. If it is only wished to examine them without their being- 
preserved, they may be mounted in a mixture of water and glycerin in 
equal volumes, protected with a cover slip, and at once placed under 
the microscope. When, however, it is wished to make a permanent 
mount they may be imbedded in glycerin jelly (Deane's medium). 
Having washed and prepared a section, and also the slip and cover, 
place a very little of the glycerin jelly on the slide, warm very gently 
and the jelly becomes liquid. Place the section carefully in the liquid 
medium, taking care that it is thoroughly immersed. Remove all air 
bubbles, place on the cover as carefully as possible, gently squeeze out 
any superfluous medium, and allow to cool. The jelly will then again 
become solid. Clean the edge of the cover glass, and coat round with 
asphalt varnish. 

329. The Germ. — The appearance and general characteristics of 
the germ itself should now be carefully studied ; for this purpose use 
the one-inch objective. 




fig. 41. — longitudinal section of germ of wheat, magnified 32 diameters. 



PHYSICAL STRUCTURE OF THE WHEAT GRAIN. 223 

The figure shown is an enlarged one, drawn from the same section as 
that given in figure 38. Notice, in the first place, that in the act of 
mounting the section, the skin has become detached from the germ, and 
also that the germ itself has split slightly near the top. At a the 
cerealin cells of the bran terminate, and only the " testa," or envelope 
of the true seed, encloses the embryo. The part of the germ marked b 
is that which forms the " plumula," or part of the young plant which 
penetrates to the surface during growth, and then constitutes the 
growing stem and leaves of the plant. From c the radicle, or rootlet, 
commences its growth, and forces its way downward into the earth. 

On that side nearest the endosperm the germ is enveloped in a thick 
skin, or epidermis, consisting of a series of elongated cells arranged 
with their longest diameters towards the endosperm. This peculiar 
structure is termed the " scutellum," and is the absorptive contrivance 
by which the germ derives sustenance from the endosperm. 

When wheat germinates, the plumula of the germ first bursts through 
its envelope, and finds itself in contact with the " pericarp," or outer 
skin of the grain (enveloping the testa). The pericarp is next ruptured, 
and the growth of the plumula proceeds outside the grain. As the 
growth proceeds, the scutellum acts by absorption, and drains the portion 
of the endosperm lying nearest it of such material as can readily be 
absorbed by the growing plant. As practically the whole of the nutri- 
ment required has thus to be obtained, the starch lying nearest to the 
scutellum is attacked at a comparatively early period, even though there 
may be abundance of other formative material of a kind which renders 
it more easy to assimilate in the more remote parts of the endosperm. 
The first evidence of any such action of germination upon the starch 
granules is generally afforded by the appearance of a number of small 
pits on the surface of the granule, these by-and-bye enlarge into fissures, 
and the starch granulose is rapidly dissolved. After a time there 
remains nothing of the granule but the outer skeleton of the starch 
cellulose, and this too, later on, disappears. An important point that 
may be mentioned in passing is that this pitting of the starch granule 
has never been obtained artificially. Experiments have been made 
with the aqueous extract of malt, and in other ways, but at ordinary 
temperatures no result has followed. Consequently, this phenomenon 
must be looked on as one that is essentially connected with the living 
functions of the vegetable cell. The obvious lesson to be drawn from 
this by the miller is that sprouted wheat (" growy " wheat) is a 
dangerous article to use. The embryo is able, during the act of ger- 
mination, to destroy the outer cellulose of the starch cells, but the 
ordinary diastasic influences of the soluble albuminoids of wheat (after 
the germ has been removed) are not capable of action on the previously 
uninjured starch granules at ordinary temperatures. 

330. Endosperm and Bran. — Attention must next be directed 
to the structure of the endosperm and the branny coatings by which it 
is enveloped. For this purpose a very thin section should be selected 
and then examined under the -J-inch. objective. 



224 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 




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U 

UJ 
Cfl 

< 



The bran of wheat is divided into the outer envelopes of the grain 
and those of the seed proper. Following these in the order of the 
letters given in the figure : — 

a — is the outer " epidermis," or " cuticle." According to Mege 
Mouries this constitutes 0*5 per cent, by weight of the whole grain. 

I) — i s the " epicarp," and amounts to about 1*0 per cent, of the grain. 

c — is the last of the outer series of the envelopes of the grain, and is 
known as the " endocarp." It is remarkable for the well-defined round 
cells of which it is composed. The endocarp amounts to 1*5 per cent, 
of the grain. 



PHYSICAL STRUCTURE OF THE WHEAT GRAIN. 225 

d — is the first of the envelopes of the seed proper, it is that to which 
reference has already been made as the " testa," it has also received the 
name of " episperm." The colouring matter of the bran occurs princi- 
pally in the episperm. 

e — is a thin membrane lying underneath the testa, and enveloping 
the cerealin cells. This membrane and the testa together form two per 
cent, of the grain. 

/ — is the layer of " cerealin " cells, so called from the albuminoid of 
that name which they contain. As may be seen from the figure, the 
cells are almost square in outline ; one is at times replaced by two lesser 
ones, as occurs immediately above the cell/. Notice particularly that 
this layer does not envelop the germ, but only encloses the endosperm. 

g — represents the layer of cellulose by which the interior of the 
endosperm is divided up into a number of cells of comparatively large 
size, these in turn being filled with starch granules, and embedded in 
gluten. 

h — shows the " hilum " of an individual starch granule. 

In order to complete the investigations of the appearance, when 
viewed under the microscope, of the various coatings of the wheat grain, 
it is not only necessary to examine these skins in section, but also, so 
far as possible, as seen on the flat. The bran of wheat can be split up 
with comparative ease into three layers, which can be successively peeled 
off from the endosperm. The first of these consists of the epidermis, or 
cuticle, and also epicarp. Following these are the endocarp and epi- 
sperm, which usually peel off together. The inner and last skin consists 
of that containing the cerealin cells. 

Take a few grains of soft red wheat and soak them for a few hours in 
warm water ; when they are sufficiently softened, take one, and with a 
fine pair of forceps strip off the outer skin and place it in a watch glass. 
When the whole of the outer skin has thus been removed, carefully 
strip off the middle layer in the same manner, and also reserve it for 
examination. The division of the inner layer from the endosperm is 
often only accomplished with difficulty ; in case they do not separate 
well, let the grain soak some time longer. 

Next proceed to examine these several coatings. Mount each on a 
slide in a drop of water (or preferably, when wished to examine the 
mount for some time, in a drop of glycerin), so that it is practically 
freed from bubbles, and lying flat and without creases. Put on a glass 
cover and press gently down. Examine with either a quarter or eighth- 
of-an-inch objective. 



226 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 




fig. 43. — outer layer of the bran of wheat, magnified 250 diameters. 



Observe in the outer layer that it consists of a series of cells some 
four to six times long as broad, and arranged longitudinally in the 
direction of the length of the grain. A portion of the outer layer is 
shown in figure 43. Notice at the one end (of the actual section, not 
the figure), the beard of the grain, and note particularly the attach- 
ment of each hair to the skin (the root). Observe also the canal 



extending about half the 
of such hairs. 



length 



of the hair. 



Figure 44 is a drawing 




FIG. 44.— BEARD OF GRAIN OF WHEAT. 



Next observe the appearance of the second layer of skin that has 
been detached ; this is shown in figure 45. 



PHYSICAL STRUCTURE OF THE WHEAT GRAIN. 



227 




r=^ 



fig. 45. — middle layer OF the bran of wheat, magnified 250 diameters. 



In this will be seen two layers of cells that are not both in focus at 
the same time, the one layer being, in fact, underneath the other. 
There are in the first place a series of long cells arranged transversely 
to the longitudinal section of bran shown in figure 42, where they are 
marked c. Because they are thus arranged around the grain of wheat 
they are frequently termed " girdle " cells. The great difference between 
looking at the same thing in one direction and then in another is 
strongly exemplified in this study of these particular cells in plan and 
in section. An instructive lesson may be gained by comparing the 
section illustrated in figure 42, with a similar section cut transversely 
instead of longitudinally. Such a section is given later in the series. 
The colour-containing cells underlie those to which reference has just 
been made. 

In the next place examine the inner, or cerealin cell, layer of the 
bran. 



228 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 




FIG. 46. 



-INNER OR CEREALIN LAYER OF THE BRAN OF WHEAT, magnified 

440 diameters. 



The cerealin cells of the bran are often referred to as being cubical ; 
that this, however, is not the fact is well shown in figure 46. They 
certainly have a square or rectangular outline when seen in section, 
whether longitudinal or transverse, but the skin, viewed on the flat sur- 
face, shows that the cells are irregular in outline, each accommodating 
its contour to that of those surrounding. 

There follows a sketch of the transverse 
wheat ; this should be carefully compared with the longitudinal section,. 
figure 42. 



section through the bran of 







FIG. 



47. — TRANSVERSE SECTION THROUGH BRAN OF WHEAT, magnified 250 

diameters. 



The actual section from which this drawing has been made is not so 
good a one as the longitudinal section, from which figure 42 was drawn. 
Viewed with a moderately high power it is difficult to get very much of 
the thickness of the section in focus at the same time ; still sufficient is 
noticed, on careful observation, to show the general structure of the 
bran. The outline of the cerealin cells is more irregular than was the 



PHYSICAL STRUCTURE OF THE WHEAT GRAIN. 



229 



■case in the longitudinal section; they are also noticed to be, in several 
instances, overlapping each other. Looking at the cells of the middle 
skin of the bran they are seen to be of considerable length, justifying 
the remarks made about them when studying their appearance as seen 
•on the flat. While, however, these middle cells are seen lengthwise, it 
follows of necessity that the ends of the cells of the outer skin must be 
presented to the eye. This sketch, ta,ken with the others, gives a tolerably 
complete idea of the microscopical structure of a grain of wheat. 

A careful study of these sections of the wheat grain and of the various 
layers into which the bran can be divided should give the miller in 
particular a clearer and more real idea than he can otherwise have of 
the nature of these outer integuments of the wheat grain, which it 
should be his object to remove. The study should not merely be con- 
fined to the drawings given in this work, but should extend to the 
actual slides themselves under the microscope. 

331. Bran Cellulose. — The bran of wheat consists largely, as is 
well known, of cellulose or woody fibre, together with a considerable 
proportion of soluble albuminous matter. Cellulose may be obtained in 
a fairly pure state by alternate treatment with hot dilute solutions of 
acid and alkali. The actual structure of the cellulose of the different 
layers of the bran possesses considerable interest, and may be studied in 
the following manner : — Strip off the different layers of skin as before 
directed, put pieces of each in a separate test-tube, and first digest for 
an hour with dilute sulphuric acid ; pour off the acid, and digest with 
caustic soda solution for another hour. Make up solutions of 1 part 
respectively of acid and alkali, and 20 parts of water. Wash the 
resulting cellulose, and mount carefully on a glass slide : examine under 
the microscope. 




fig. 48. — cellulose of outer skin OF bran, magnified 250 diameters. 
This is rendered almost transparent, and presents no striking 
differences in structure from the orignal skin. 



230 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 




fig. 49. — cellulose of middle skin of bran, magnified 250 diameter?. 

In this again the resemblance to the skin before treatment is very 
noticeable. One special point of interest occurs in this drawing ; the 
two layers of cells to which reference was made when previously speak- 
ing of the appearance of this layer have become separated. The upper 
cells extend over the whole field, while the lower or pigment layer is 
stripped from the one portion. The result is that the distinction 
between the two is seen very clearly. 

As the cerealin layer or inner skin of the bran contains so large a 
quantity of albuminous matter, it will readily be imagined that treat- 
ment with alkali will cause considerable difference in the appearance of 
this layer. 




fig. 50.- 



cellulose of cerealin layer of bran, with portion of Cerealin 
remaining, magnified 440 diameters. 



PHYSICAL STRUCTURE OF THE WHEAT GRAIN. 



231 



In figure 50 such a specimen is shown ; it will be noticed that a 
portion only of the cerealin remains, the majority having been removed 
by the action of the caustic soda. 




fig. 51.— cellulose of cerealin layer of bran, with only the slightest trace of 
Cerealin still remaining in some of the cells, magnified 440 diameters. 



This figure shows in most striking fashion how small a proportion of 
the interior layer consists actually of cellulose. Reviewing the whole 
three layers, one finds that the outer one is largely composed of cellulose, 
and consequently is condemned as an article of human food, even by the 
Bread Reform League. The middle layer contains less cellulose, but 
contains a high proportion of colouring matter. The proportion of 
cellulose in the inner layer is still less, but the amount of cerealin is 
high. It has been already stated that this body is injurious to the 
flour, inasmuch as it exerts considerable action on broken starch gran- 
ules. There are therfore cogent reasons for the non-admission of any 
part of the bran into the flour. 

332. Cellulose Of Endosperm. — On taking a grain of wheat 
and carefully cutting off the bran so as to have a piece of the endosperm 
only, and treating this interior portion of the grain with acid and alkali, 
a trace of cellulose is obtained which shows no distinctive organisation 
under the microscope. The student will do well to verify this fact for 
himself. Let him also treat small quantities of different varieties of 
flour in a similar fashion, and examine the remaining cellulose. Such an 
inspection is calculated to teach much concerning the success of the 
operation of milling. He will be able to see whether or not the number 
of small particles of bran in the flour is large. He will also learn 
whether or not the bran itself is intact, or whether portions of one or 
other of the surfaces have been removed and ground up into the flour. 



232 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



m, the author would add, do not be satisfied with reading 
descriptions of these things. An attempt has been made to specify the 
salient points of each slide, but a careful examination of one only will 
teach more, and yield more to think on, than will a whole chapter 
devoted to wheat microscopy. It is gratifying to know that study of 
this kind has already engaged the serious attention of members of the 
milling craft ; thus, out of the drawings given in this series, a number 
have been made from microscopic sections cut and mounted by a well- 
known miller, to whom the writer is indebted for them. 



CHEMICAL COMPOSITION OF WHEAT. 



233 



CHAPTER XV. 



CHEMICAL COMPOSITION OF WHEAT. 



333. Principal Constituents of Cereals.— Proximate analysis 

of the cereal grains shows that they contain as their principal constitu- 
ents — fat, - starch, cellulose, dextrin, one or more sugars ; soluble 
albuminous bodies, consisting of albumin, legumin and cerealin ; in- 
soluble albuminous bodies, consisting of myosin, glutin, mucedin, and 
fibrin, which together constitute gluten; mineral matters, consisting 
principally of potassium phosphate, and water. 

The following, according to Bell, is the average composition of the 
different members of the cereal family : — 



Constituents. 


Wheat. 


Long- 
eared 
Barley. 


English 
Oats 


Maize. 


Rye. 


Carolina 
Rice, 

without 
husk. 


Winter. 


Spring. 


Fat 

Starch 

Cellulose 

Sugar (as Cane) 

Albumin, &c,"l 

! insoluble in al- J- 

cohol ...J 

Other nitro- ^ 
genous matter. {_ 
soluble in al- 1 
cohol ... J 

Mineral matter 

Moisture 

Total 


1-48 

6371 

3-03 

2'57 

IO70 
4-83 

i-6o 
12-08 


I- 5 6 
65-86 

2-93 
2*24 

7-19 

4-40 

174 
14-08 


1-03 

63-51 
7-28 

i'34 
818 

3-28 

2-32 
13-06 


5'14 
4978 

13*53 
2-36 

IO-62 
4*05 

266 
n-86 


3-58 
64-66 

i 86 
1-94 

9-67 

4-60 

! 35 
12-34 


i*43 
61-87 

3-23 
4-30 

9*78 

5-09 

1-85 
I2'45 

ICO 'OO 


0-19 

77-66 

Traces. 

0-38 

7'94 

1-40 

0-28 
12-15 


I OO "00 


100*00 


100*00 


IOO'OO 


ioo-oo 


ioo-oo 



Before giving detailed analyses of various samples of wheat, a descrip- 
tion of the effect of each constituent on the character of the wheat will 
be of service. 



234 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

334. Pat. — As far as is at present known, the quantity of fat in 
wheat is not a very important element in determining its value. Fat 
is of course an important food stuff, and as such is of service. The 
germ of flour contains a very high percentage of fat, and when removed 
must necessarily lessen the percentage of this body present. 

335. Starch. — This makes up the principal part of the grain, and 
in the analyses above given, amounts to 63'71 and 65*86 in the two> 
wheats. In these analyses the starch was probably determined by 
difference ; that is, the percentage of the other constituents was sub- 
tracted from 100, and the remainder considered to be starch : the 
quantity of starch will therefore naturally be the complement of the 
other bodies, rising when they fall and falling when they rise. Starch 
is of course of great importance as being the principal food-stuff of 
bread : in sound wheat the starch granules are whole, while in wheat 
which has sprouted, or heated unduly through clamp, the starch granules 
are pitted, and often fissured. The result is that their contents become 
more or less changed into dextrin and sugar. 

336. Cellulose.— This substance is of considerable service to the 
plant ; but to the miller it has no value, as being useless as an article 
of food, he endeavours to keep it out of the flour. As th« cellulose is 
found principally in the bran, the thinner skinned wheats will yield, on 
analysis, less cellulose. Judging the cellulose alone, the less quantity 
present the better is the wheat. 

337. Dextrin and Sugar. — Dextrin exists in sound wheat in 
but small quantity ; but when hydrolysis of the starch has set in, the 
percentage may considerably increase : in wheats or flours the presence 
of large quantities of dextrin would be decidedly objectionable. Sugar 
is always present to a slight extent in wheat. Bell states that the 
sugar corresponds in properties to cane sugar, as it does not reduce 
Fehling's solution, but may be readily inverted by sulphuric acid. Bell 
extracts the sugar with 70 per cent, alcohol, and so prevents any action 
on the sugar of the albuminoids. The author finds that on extraction 
with water, the sugar invariably produces more or less precipitate with 
Fehling's solution ; the amount of precipitate being increased by treat- 
ment with sulphuric or hydrochloric acid. Paragraph 270, chapter XI.,, 
gives some results of sugar determinations in the aqueous extract of 
flour. The explanation of these results seems to be that, in perfectly 
sound wheat or flour, small quantities of cane sugar, only, exist. In 
unsound wheats or flour, in which the starch has been subjected to* 
diastasis, maltose may also be detected. Wanklyn makes the useful 
suggestion that estimations of sugar should be made in both aqueous 
and alcoholic extracts : unsoundness in flour would be indicated by the 
presence of an increased amount of maltose in the alcoholic extract. 

Assuming the correctness of Bell's statement that sound wheat sugar- 
does not reduce Fehling's solution, an alcoholic extract of sound wheat 
should give no precipitate with that reagent. Any maltose therefore in 
an alcoholic extract is the measure of diastasis of the starch of the grain 
that had occurred previous to analysis. If the flour be then mixed with 
water, and allowed to stand for a definite time, and then the maltose 



CHEMICAL COMPOSITION OF WHEAT. 235' 

estimated in the aqueous extract, the difference between the amount 
obtained in this estimation and the former one would be a measure of 
the quantity of soluble starch, arising from fissured granules, present in 
the flour. A series of comparative estimations of this kind would be of 
service. 

As the sugar of a flour affords the saccharine body necessary in fer- 
mentation, the presence of this compound in small quantity may be 
tolerated, but as before pointed out, it should consist principally of cane 
sugar, the presence of much maltose being evidence of unsoundness. 

338. Soluble Albuminoids. — In technical wheat analysis no 
attempt is made to separate the albumin from the legumin. In the 
following analyses these bodies are estimated by what is known as the 
albuminoid ammonia process, in a portion of the aqueous extract of 
■ the flour, of which, in common with other analytic methods, a descrip- 
tion is given hereafter. As has been already stated, these bodies have 
a serious action on starch, and also on gluten ; under the influence of 
yeast, during fermentation, they act on the starch and convert that 
body into dextrin and maltose. Both flours and wheats are therefore 
to be preferred in which the soluble albuminoids are relatively low. In 
the case of wheat it is somewhat difficult to form a judgment, because 
the bran and germ contain considerable quantities of soluble albuminoids ; 
as these are removed in the operation of milling the proportion differs 
somewhat in the wheat from that in the dressed flour. It is in damp 
years and wet climates that inferior wheats are grown ; the excess of 
moisture, and lack of warm, dry sunshine, leaves the grain damp, and 
also leaves the albuminoids in the soluble condition, instead of thoroughly 
ripening the grain, and thus causing them to assume the insoluble- 
form. 

From time to time attention has been directed to the problem of 
artificially drying wheats. With some samples of wheat this is 
practically a necessity, as otherwise they are absolutely unfitted for 
flour producing purposes. A gentle kiln-drying at a temperature of 
from 100° to 120° F., by driving off the excess of water, averts its 
degrading action on the gluten, and causes the wheat to yield a sounder 
and stronger flour. The drying is necessarily accompanied by loss of 
weight ; against this must, however, be set the improved quality of the 
flour. In connexion with this, attention is directed to the paragraph on 
artificially drying wheats and flours, in the next chapter. 

339. Soluble Extract. — In the following analyses by the author 
the percentage of "soluble extract" is in most cases given. This 
represents the proportion of the wheat or flour soluble in cold water. 
The sample is shaken up with water repeatedly during half an hour, 
then filtered from the solid matter, the clear liquid evaporated, dried at 
100° C. (212° F.) and weighed. This extract consists of soluble 
. albuminoids, sugar and dextrin, and potassium phosphate. Considerable 
importance attaches to the amount of soluble extract, as being the 
measure of the amount of degradation of the gluten and starch of the 
Avheat or flour ; consequently an excess of soluble extract indicates un- 
soundness. On the other hand, a very low percentage of sugar in a. 



236 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



flour or wheat is accompanied by an absence of that sweetness charac- 
teristic of the best flavoured wheats and flours. 

340. Insoluble Albuminoids, Gluten.— The insoluble albu- 
minoids are, for practical purposes, estimated by doughing the flour, and 
washing away the starch, leaving behind the tough and elastic gluten. 
The gluten of wheat is of great importance, as being that constituent 
which imparts to wheaten flour its remarkable property of rising into a 
light and spongy loaf. The gluten is usually weighed both in the moist 
or wet state, and also when dry ; it weighs from 2 -7 to 3 times as much 
when moist as dry. As the gluten of wheat is that constituent which 
causes the flour to be a strong flour, wheats to be of high quality should 
contain a high percentage of gluten. This, however, is not of itself 
sufficient ; the glutens of different wheats vary not only in quantity but 
in quality — some glutens are tough and elastic, others are soft and 
" rotten." These latter yield weak flours, and consequently bread which 
is not well risen ; further, the quantity of water they are capable of re- 
taining is but small. They as a result produce a comparatively low 
number of loaves from a sack of the flour. The gluten then should not 
only be present in considerable quantity, but should also be highly 
elastic. 

Between the amount of gluten and of soluble albuminoids in a wheat 
a close relation exists. With an increase of total albuminoids, both the 
soluble and insoluble varieties will simultaneously rise in amount. In 
interpreting analytical results, high soluble albuminoids should not be 
considered alone — they are the natural concomitants of high total 
albuminoids and gluten. But where the soluble albuminoids are high, 
and the gluten low, then distinct evidence of a low grade or unsound 
wheat is afforded. 

The aleurometer is an instrument designed for the purpose of estimat- 
ing the elasticity of gluten ; the higher the figures obtained by its use, 
the more elastic the gluten is supposed to be. 

341. Ash. — This gives the quantity of mineral matter present in a 
wheat or flour ; the ash consists principally of potassium phosphate, a 
substance of considerable value from a nutritive point of view; the 
mineral matter of wheat is contained principally in the bran. 

342. Water. — The water of wheat is found to be mostly associated 
with the starch of the grain ; that body is extremely hygroscopic, and 
can only be obtained actually free from water by prolonged and careful 
drying. The quantity of water in flour and wheat does not vary within 
very wide limits, the highest percentage being about 15, and the lowest 
about 8 per cent. The question of importance is the influence of the 
water on the quality of the grain or flour, and the interpretation to be 
placed on such results as are here given. As may readily be supposed, 
a wheat that is grown either in a naturally damp climate, or during an 
unusually wet season, contains more water than one grown under the 
opposite conditions. Taken into consideration without reference to the 
other constituents of the grain, a large proportion of water is to be 
deprecated, for the very simple reason that water is scarcely worth pur- 
chasing at the price given for wheat or flour. This, however, is not 



CHEMICAL COMPOSITION OF WHEAT. 237 

the only objection to the presence of a large percentage of water ; a 
much more serious objection is based on the fact that such high propor- 
tions show that the wheat is unsound, and that in all probability the 
other constituents will not be of the most promising character. In the 
first place, damp wheats and flours favour the development of those 
organisms which produce mustiness and acidity. In the presence of 
excess of moisture, too, the gluten of flour is rendered soluble in part> 
and also loses its elasticity. Further, more or less of the starch will be 
found to have been degraded into dextrin and maltose by diastasis. 

343. Analyses of English and Foreign Wheats.— The 

analyses embodied in the following tables are selected from those of 
wheats analysed by the author for insertion in his " Confidential Report 
on Wheat and Flour Supply," particulars of which publication are given 
in an advertisement at the commencement of book : — 



-238 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



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CHEMICAL COMPOSITION OF WHEAT. 



239 



ir. 

< 


Grown on good heavy land in Essex, 
1883 ; fairly farmed ; delivered by 
farmer at 66*5lbs. per bushel. 

Grown in Devon, about two miles 
from sea ; considered by sender to 
have probably been injured during 
the blooming period. 

Grown in the neighbourhood of Bo- 
roughbridge. 

Grown at Hampstead. 

Wheat of splendid quality, but in 
opinion of miller, who forwarded 
it, not very strong. 


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Essex Rough Chaff, White 

Red Chaff 

English Red 

Rough Chaff 

Red Square Head 

Red Lammas ... 

Wheat from the Vale of Taunton ..... 

Scotch E. Lothian 

Rough Chaff, grown at Newbury ... 

Red Lammas ... 

Herts, White 

Nursery, grown at Lickhampstead . . . 
Rough Chaff ,, Compton, Berks 
Trump ,, Newbury... 

White 

Red 

Red Chaff, from Sidbury, Devon ... 
Red Nursery ,, ,, ,, 
Square Head, from S. Coast, Devon 


6 
55 


O hi IN tO Tf- IOVO tv.00 O\0 "«fO* lOvO t^OO 
M IN N N« N« INNNtOfOCOtOfOfOtOtOtO 



240 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Nos. 1-18 inclusive were analysed in April, 1884; they are, except 

where otherwise mentioned, 1883 wheats. 
Nos. 19-27 inclusive were analysed in September, 1884, and are all 

1883 wheats. 

Nos. 28-38 inclusive were analysed in November, 1884, and are all 

1884 wheats. 

Reviewing Nos. 1-18 as a whole it may be remarked that the moisture 
is high ; as might be expected No. 18 heads the list. The soluble 
extracts and albuminoids average a somewhat high figure. Taking the 
glutens throughout these are lower than in foreign wheats, the highest 
figure being only 8*21. As might be expected the Revitts are exceed- 
ingly low ; the trace of gluten was so small that it was practically 
impossible to recover it from the bran. Of the other wheats, Nos. 6 and 
18 contains the lowest quantities of gluten. 

Samples Nos. 19-27 call for no special remark, representing as they 
do the class of wheats largely used, particularly in the south of Eng- 
land, in the manufacture of flour. It is interesting to note the 
variations in the character of the same variety of wheat when grown in 
different localities, and under different conditions. Nos. 19 and 20 
were considered by sender, a miller whose flours are familiar in the 
London market, to be exceptionally fine samples of their kind. No. 21 
is of interest as showing the composition of a wheat damaged during 
growth. 

The English wheats of the harvest of 1884 were of exceptionally fine 
quality. The samples given were selected from the South and Western 
Counties. Compared with the series of English and Scotch wheats of 
1883 harvest the moistures run much lower, the average being 13*55 
against 14-82 in the 1883 wheats. The same remark applies to the 
soluble extract and soluble albuminoids. The average of the glutens is 
also somewhat lower, being 6*40 against 6*87. The lowest gluten of the 
1883 series was 5*00 in a Scotch West Country wheat, this had also the 
highest moisture ; like the Scotch sample, No. 38 in the new series is 
grown in a damp climate, S. Devon, and yields the same percentage of 
gluten. The highest gluten, 8*61, is yielded by a sample of white 
wheat, the highest of the 1883 wheat being a sample of rough chaff 
grown at Didcot, and containing 8*21 of gluten. 



CHEMICAL COMPOSITION OF WHEAT. 



241 



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CHEMICAL COMPOSITION OP WHEAT. 243 

The foreign wheats are naturally more varied than those grown in 
England and Scotland. The Russian wheats, as a class, show a higher 
percentage of gluten than do the American. Readers may make an 
interesting comparison between the moistures of wheats and the flours 
produced from them; the comparison may also be extended to the 
glutens. 

Indian and Persian wheats have of late been receiving considerable 
attention from millers, and also bakers, who are equally interested in 
the wheat supply of the country. The Indian wheats are characterised 
as a class by being very low in gluten, and this is accompanied by a low 
percentage of moisture. The meals, when worked up with water, are 
almost sandy in their nature ; it is only after standing some little time 
that they begin to acquire the characteristic ductility of wheaten flours, 
the Persian wheats are decidedly richer in gluten than the Indian : 
this holds especially with the clean Persian, No. 68. 

No. 79 was forwarded by the L.C. Porter Milling Co., of Winona, 
U.S.A., and is the wheat from which flours Nos. 8 and 9 were made. 
The higher line of figures represents the results obtained on allowing 
the dough to lie two hours before extracting the gluten. One very 
special feature of this wheat, and also the flours produced from it, was 
the extreme slowness with which they absorbed water and became 
thoroughly softened and hydrated. 

Wheat No. 80 was grown on land 400 to 800 miles west of 
Winnipeg, Manitoba, and is that which was recently supplied through 
the Editors of "The Miller" and the "British and Foreign Con- 
fectioner" to the leading millers and bakers of the country. The 
comparatively high moisture, soluble extract, and albuminoids, are 
indications of the cold climate in which it has been grown. The com- 
parison between this sample and No. 79 are of interest. The Canadian 
flours referred to in a subsequent table were made from this wheat. 

344. Average Composition of American Wheats.— The 

following table gives the average composition of American wheats, 
according to Richardson, Chemist to the United States Department of 
Agriculture. The carbohydrates consist of the starch, dextrin, and 
sugar. The total quantities of albuminoids are given, being derived from 
the percentage of nitrogen found : — 



244 



CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 



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COLOUR OF FLOURS. 245 



CHAPTER XVI. 

CHEMICAL COMPOSITION OF FLOUR AND OTHER MILLING PRODUCTS. 

345. In addition to its purely chemical composition, flour possesses 
certain physical properties which are of the highest importance to the 
baker, and consequently to the miller. These are " Colour " and 
" Strength." Flavour may also be mentioned, but this is essentially 
rather a matter of the palate than of chemical analysis, hence a judg- 
ment of the flavour of flour is best made by the actual consumer. 
These three properties of Colour, Strength, and Flavour, together with 
certain side issues connected with them, largely, if not entirely, 
determine the commercial value of a sample of flour. The baking and 
milling experts are, through long experience, capable of judging these 
qualities of a flour with wonderful accuracy ; but the methods used in 
so doing have been in most cases of the crudest description. Further, 
however accurate may have been the results obtained, there has been 
no precise method of registering them for future reference, nor for 
instituting comparisons between the results obtained by one observer 
and those of another. In order to do this, these properties must in 
some way be expressed numerically. 

346. Colour. — Every miller and baker will be acquainted with 
the ordinary method, devised by P£kar, of determining the colour of a 
sample of flour by compressing a small quantity into a thin cake or 
slab, which is wetted and allowed to dry. The depth and character of 
the colour are then observed. This test has been in use for some time, 
and answers admirably the purpose of comparing the relative colour of 
two or more samples. There is, however, this difficulty : while one 
sample may be considered good, another bad, and a third indifferent, there 
is no actual standard of comparison with which each may be compared, 
and so its colour expressed in definite terms. For scientific purposes it 
has been long felt that some standard scale of colour was necessary, so 
that flours might be compared with it, and then the results expressed 
numerically, thus fulfilling the above-mentioned condition. Such a 
scale would require to be made of colours that do not bleach or undergo 
change on keeping ■ the tint should as closely as possible resemble that 
of flour, and the character of the coloured surface should resemble that 
of flour after being wetted and dried. The author believes that, as the 
result of many months' work and experiment, he has succeeded in pro- 
ducing a scale that satisfies these requirements. He wishes it to be 
distinctly understood that all credit for devising the method of testing 
is due to P£kar. He is simply responsible for the production of the 
scale for purposes of comparison. 



246 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

Flours differ, not only in depth of tint, but also in actual colour. 
For most purposes of comparison they may, however, be divided into 
two varieties, the prevailing tones of which are respectively grey and 
yellow. The greater number of flours fall into the grey class, while a 
few of the very finest patents, represented notably by the best 
Hungarian brands, have a rich yellow tint. 

The colours selected for the scale are — first, a greyish yellow ; and 
second, a purer yellow tint. A scale of each colour is constructed : 
they are termed the Grey and Yellow Scales respectively. The Grey 
Scale starts with a very light tint, marked " 1 " and finishes with a dark 
tint, marked " 16." The whole of the tints have an intensity propor- 
tional to their number, thus number 2 is exactly twice as dark as 
number 1, while number 8 is four times as dark as number 2. 

The Yellow Scale, being intended for patent flours only, is not 
extended so far as the Grey Scale. It is difficult to compare the two 
scales with each other, because the colours are dissimilar ; but, in 
intensity, number 1 yellow is about equal to 1 \ grey ; number 10 yellow 
is three times as dark as 1 yellow, and about equal in intensity to 4J 
grey. The colours deepen in intensity by regular intervals from 
number 1 to number 10 yellow. 

In preparing the scales, special precautions are taken to ensure that 
the tint obtained are of mathematically accurate intensity. Each sheet, 
after being tinted, is carefully examined, and any which appear in the 
slightest degree irregular are rejected. Those finally approved are 
then cut into pieces of the requisite size, and mounted in a suitable 
case. 

In testing the flours for the subsequent analyses a number were 
taken at the same time, placed on a plate of zinc, and pressed so as to 
give the flour a smooth surface. The samples were then dipped in a 
sloping direction into water, allowed to remain some ten or twelve 
seconds, withdrawn, placed aside, and allowed to dry at the ordinary 
temperature. In reading the colour it was first determined whether 
the flour corresponded more closely to the Grey or Yellow Scale ; then, 
by careful observation, the numbered tint was selected which agreed 
with the flour in depth of colour. If the sample fell between any two 
tints, the colour was indicated by a fraction, as for instance, 2*5 or 3*4. 
Having gone through the whole of the samples being tested, and having 
expressed their colours in numbers, a second examination of the series 
was made. Those flours which approximated in colour were tested against 
one another — thus, suppose two had been marked 7*0 G. ; it was then 
determined whether they agreed with each other, if so they were passed, 
but if not they were again compared with the scale and numbered 
respectively, 7'0 and 7*1, or whatever other numbers were deemed to 
most accurately represent the colour. In this way, by a system of com- 
parison and counterchecking, the absolute value of the colour was 
arrived at as closely as possible. 

In some samples the colour was intermediate in character between 
the two scales ; thus, some flours were grey, with just a tint of yellow ; 
others were very nearly like the Yellow Scale, but rather grey beside it ; 
these properties where indicated by the use of two letters, thus 



COLOUR OP FLOURS. 247 



" 7 '5 G.y." This means that the flour approached 7*5, on the Grey 
Scale, in depth of tint, but that it was rather yellower than the scale, 
but still nearer the grey than the yellow series of tints. On the other 
hand, 6 Y.G. means that the colour was matched and numbered on the 
Yellow Scale, but that it was somewhat grey in character. 

In connexion with this matter of colour a question arises as to how 
far the colour of a flour, as determined by this test of Pekar's, agrees 
with that of the baked loaf. Millers who have given the subject 
careful attention, state that at times test loaves baked from the 
flours under examination have their colours in just the reverse order to 
those of the original flours when compared by Pekar's method ; this is 
stated to occur more particularly with patent flours. This must of 
necessity be taken into account when determining flour colours by this 
process. In connexion with the baking test, as a means of judging 
the colour of a sample of flour, it must be remembered that from the 
same flour not only will two bakers very often get bread of different 
degrees of colour, but also that one and the same baker may perceptibly 
improve the colour of his loaf by modifications in his methods of 
panification. Now, under these circumstances, it is evident that a 
baking test cannot be viewed as an absolute one, so far as colour is 
concerned. As will be hereafter explained, a falling off in colour during 
fermentation is due to certain chemical changes, resulting from the 
action of yeast and diastasis — hence, if two flours have by Pekar's test 
the same colour, and the one produces a lighter loaf than the other, then 
No. 2 flour is less capable of withstanding the fermentative changes 
than is the other. It is possible that by shortening the length of time 
which this second flour is fermented that its colour may be brought on 
an equal to that of the first. If the two flours be tested for Strength 
and Stability in the manner to be subsequently described, it will in all pro- 
bability be found that the second possesses the latter quality in less 
degree. 

Notwithstanding that discrepancies of this sort may at times occur 
between Pekar's test and the results of baking experiments, the author 
lays great value on this test of Pekar's, because it gives the absolute 
colour of the flour only, uncomplicated with effects due to fermentation. 
The baker, and indirectly the miller, are very much at the mercy of the 
journeyman baker. On some day a heavy dark coloured batch of 
bread is produced ; the journeyman at once says the flour is wrong, or 
the yeast is bad, never a suggestion that the fault may be due to 
mistakes or accidents in fermentation. The baker often finds himself in 
doubt as to what is really the cause of the inferior quality of the bread ; 
let him, for one thing, make this Pekar's test on the flour of the 
particular batch, against that he has been previously using. If the last 
lot of flour is decidedly lower in colour he may fairly ascribe the fault 
to a change in the flour with which he is supplied. On the other hand, 
if the two are indistinguishable, the probabilities are greatly in favour 



of the fault resting with the fermentation and general working of the 
dough. He may now go a step further, and test for Strength and 
Stability ; if they are the same in the two flours he may be morally 
certain that the fault is not in the flour, but in the yeast or the manipu- 



*248 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

lation during fermentation. But should the flour which produced 
the darker coloured loaf be the less stable, then very possibly the falling 
off in colour is due to the flour. The importance of these tests is not so 
much the simple valuation of the particular flour which may be under 
examination, as the light which they throw on whether it is the flour or 
the quality of yeast and mode of fermentation which is responsible for 
the inferior loaf. One of the baker's greatest difficulties when anything 
goes wrong with his bread is to know what it is ; until he ascertains 
that, any attempts at improvement are so many leaps in the dark. 

In the case of patent flours, which do not produce breads of the cor- 
responding colours, the author would again suggest the making of 
stability tests as well : he is strongly of opinion that the instances will 
be very few in which the falling off in bread-colour, as distinguished 
from flour-colour, is not accompanied by loss of stability. He would 
suggest in such cases that a shorter period of fermentation should be 
employed, with the belief that an improved bread-colour would result. 
Such a flour would also arrive at maturity in dough in a shorter time 
so far as other changes are concerned. 

The statement is at times made by bakers, that the bread from a 
particular flour is improved in colour by a longer time in fermentation. 
The author has never personally investigated this point, but is of opinion 
that no actual bleaching of dough can thus occur. It is quite possible 
that instead of a chalky whiteness a flour may, by longer fermentation, 
develop a rich yellow bloom. 

347. Strength. — The Strength of a sample of flour is one of the 
most important properties it possesses, and its determination is of the 
utmost importance to both miller and baker. It not only governs the 
yield in bread of the sample, but also affords evidence of its other quali- 
ties, especially its soundness. For, if with any particular variety of 
wheat, the strength of the flour falls below the average, there is every 
probability that the wheat is through some cause unsound. Hence, 
strength determinations are valuable in several respects. Although not 
always applied in precisely the same sense, for our present purpose, 
Strength may be defined as the measure of the water absorb- 
ing and retaining power of the flour, or of the water absorbed 
by the flour in order to produce a dough of definite consis- 
tency : it always being understood that the dough shall be capable of 
yielding a well-risen and properly cooked loaf without clamminess. 
" Strength " is also sometimes used as the measure of the capacity of a 
flour for producing a well-risen loaf. Although this means something 
different from the former definition, yet the two qualities generally go 
pretty well together. In order to avoid misunderstanding, it must be 
understood that when the term Strength is here used it is in reference 
to the water absorbing capacity of the flour. 

Undoubtedly one of the best methods of determining the strength of 
a sample of flour is by doughing it and then judging by the consistency 
of the dough. The dough may be tested in this manner shortly after 
being made up, and again after an interval of some hours. A more or 
less accurate judgment is thus formed of the water-absorbing power of 
the flour when first made into dough, and also its capacity for resistance 



STRENGTH OF FLOURS. 249 



to the changes which take place in the constituents of flour while 
standing for some time in a moist condition. The unfortunate point 
about such determinations is that, judging by the appearance and stiff- 
ness of a dough, is exceedingly uncertain : one person's own judgment 
is not at all times alike, and the difficulty is multiplied infinitely when 
an attempt is made to compare that of several persons. Again, there is 
the fact that for all purposes of exactitude it is essential that some 
means shall exist for expressing results in actual figures. 

Finding the problem in this state the author has devised and patented 
apparatus, which has as its object the determination of Strength, and 
giving a numerical expression of the result. The starting point was to 
decide on some mode of expressing strength : the first idea was to make 
use of the number of quartern loaves of bread that could be produced 
from a sack of flour. But here the difficulty occurred that different 
bakers are in the habit of weighing their bread into the oven at different 
weights, to say nothing about the possibilities of different weights when 
the bread leaves the oven. Further, the use or non-use of " fruit " 
renders this method of considerable uncertainty. There is again the 
fact that some bakers work with slacker doughs than do others. , 

Thorns, of Alyth, has made some very important experiments on the 
strength of flour by the doughing test. He has adopted the method 
of taking 1 J oz. of flour and measuring the water in drams : in a most 
valuable table published by him, he gives the results of such tests, in 
loaves per sack and barrel, with quantities of water, varying from 8 to 
16 drams. The tabulated estimate of results per sack provides for loss 
in working, the actual figures given having been determined by the 
corresponding baking tests with 280 lbs. of flour. 

Harris, a well-known London authority on baking, states that, on 
making a series of baking and also doughing tests on flour, the former 
tests up to the baking stage agree with the tests made by Thorns' 
doughing method ; but that great discrepancies are shown after baking, 
principally because it naturally follows that the higher the percentage 
-of water absorbed, the greater will be the loss by evaporation in baking. 

These tests he regards as showing that calculations based simply upon 
bow much water any given flour will absorb, may be entirely upset 
when the bread made from such flour is submitted to the test of weigh- 
ing after leaving the oven. 

Thorns' table provides for loss in working, but is throughout calcu- 
lated on the basis of 70 oz. of dough being weighed into the oven for 
each 41b. loaf ; no allowance is therefore made for different amounts of 
loss in the oven. As Harris remarks, the loss, by evaporation in baking, 
naturally increases with the percentage of water present in the dough. 

But although Harris' baking tests do not agree in actual weight of 
bread with that estimated from Thorns' table, they yet show that the 
flours which yielded highest and lowest results by Thorns' doughing 
test, also yielded highest and lowest results in bread ; thus establishing 
the trustworthiness of the principle of the doughing test, although not 
altogether confirming Thorns' estimate of actual bread yield. 

After considering several possible modes of expression, the decision 
-arrived at by the author was to give the quantity of water that a 



250 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

definite weight of the flour took, in order to produce a dough of definite 
and standard consistency. By almost universal consent the standard of 
weight of flour would, in this country, be the sack of 280 lbs., while 
water can be conveniently expressed in quarts. The quart being the 
quarter of a gallon, and the gallon weighing 10 lbs., render it easy 
to convert quarts into either gallons or lbs. It will be noticed that the 
adoption of this standard does not touch on the contested question of 
loss of water in the oven. 

348. Strength Burette. — The operation of doughing resolves 
itself into taking any convenient quantity of flour, and adding 
sufficient water to it to make a dough of normal stiffness, and then 
calculating out the water employed into the proportion of quarts per 
sack. The simplest way of doing this is to fix on the quantity of flour,, 
and then make a measuring instrument for the water ("burette" or 
11 pipette "), which shall be graduated so that each division represents a 
quart of water per sack. Such a measuring instrument is the first part 
of the patented apparatus ; in using it, the flour is weighed out, and 
the quantity of water run in is at once read off, without any calculation 
whatever, as quarts per sack. The practical advantages of this method 
are evident, as from a small doughing test a baker can at once direct 
how much water is to be added per sack of any particular flour. 

349. The Viscometer. — Having made the dough, the next thing 
is to estimate its consistency. This is the more difficult, as different kinds 
of flour produce doughs of different character. Thus, a spring American 
flour will yield a dough whose essential characteristic is rigidity ; a 
Hungarian flour yields a soft dough, but one which, nevertheless,, 
possesses most remarkable tenacity. Any instrument for measuring the 
consistency of dough must take into account these two somewhat opposite 
characters, giving each its proper value. The resistance of the dough to 
being squeezed, and its resistance to being pulled asunder, must both be 
taken into account. The second part of the patented apparatus consists of 
an instrument for definitely measuring the viscosity of dough. This is 
effected by forcing a definite quantity of dough through a small aperture, 
and measuring the time taken in so doing, the force being constant. The 
machine for making this measurement is termed a "Viscometer," literally, 
a measurer of viscosity. It is so arranged that, in doing the work of forcing" 
the dough through the aperture, both the stiffness and tenacity of the 
dough are called into play as resisting agents. The consequence is that 
a very soft and tenacious dough may prove its viscosity to be as great 
as that of a stiff dough with comparatively little tenacity. Un- 
doubtedly this is in keeping with the observed facts of baking, for, as is 
often said, certain flours will bear being made much slacker than 
others ; that is, their tenacity as dorgh more than makes up for their 
comparatively little stiffness or rigidity. 

The viscometer consist essentially of a cylinder, having a weighted 
and graduated piston, and an aperture through the bottom for the exit 
of the dough ; the stiffer the dough the more slowly does the piston 
descend. Since the first instrument was made, a number of alterations- 
and refinements have been introduced, with the object of diminishing 



STEENGTH OP FLOUES. 251 



certain causes of error which were revealed on experiment. In its 
present form, the author is satisfied that the instrument is affected in its 
working by the condition of the dough, and that only ; further, that it 
takes cognizance both of the tenacity and the rigidity of the dough. 
It is claimed for the viscometer that it affords a means of absolute 
measure of these two qualities of stiffness and tenacity. In certain cases 
where two doughs have been submitted to the judgment of bakers, and 
then tested by the viscometer, that judged the softer to the touch has 
been registered by the viscometer as the dough of greater consistency. 
The very simple explanation is that it is difficult to form an accurate 
judgment of tenacity by handling a small piece of dough. Flours which 
exhibit this particular combination of softness and tenacity, are just 
those which bakers would say require to be worked slacker than others. 
Consequently, even in these instances, the viscometric measurement 
affords a valuable indication of the working water absorbing capacity 
of the flour. Millers and bakers who have seen the apparatus at work 
endorse this opinion. In using the instrument, the dough is first put 
into the viscometer, and the time which the piston takes to travel 
between two of its graduations is noticed. 

It is obvious, that the first consideration with regard to such a mode 
of testing is, whether or not it really gives an indication of the yield of 
bread of which each particular flour is capable. The opinion of millers 
and bakers generally is, that doughing a flour shows, as no other method 
can, the strength of a sample of flour. Experiment has demonstrated, 
however, that the stiffness of a sample of dough depends on a number 
of conditions. It is first of all affected by the amount of kneading to 
which the dough is subjected ; further, as the length of time, since the 
flour and water have been mixed, increases, the stiffness of the dough 
varies. During this time two sets of changes are going on ; first, the 
water added is being absorbed by the starch and gluten particles of the 
flour : this causes an increase of stiffness, until this absorption has 
ceased. Then, in the next place, the gluten begins to soften, and so the 
dough becomes slacker. Bakers partly judge of the quality of a flour 
by the rate at which it falls off during fermentation : it being well 
known that some flours produce doughs which become slack more 
quickly than others. If it were practicable, a good test would be to 
run the dough through the viscometer after it had fermented for some 
hours : but as the dough has then become spongy, trustworthy results 
could not be obtained. A convenient measure of the rate of this de- 
gradation is furnished by letting the dough, made from flour and water 
only, stand for twelve or twenty-four hours and then testing its strength. 
The standing in this way has much the same effect as has fermentation ; 
consequently the doughing test after standing affords valuable informa- 
tion as to the stability of the flour during fermentation. By means, 
therefore, of tests made after the lapse of some hours, the relative per- 
manency in dough, of different varieties of flour, may be shown. Such 
testings also indicate whether a flour should be used in the sponge or 
dough stage, or whether it is best fitted for long or short processes of 
fermentation ; thus a flour which was fairly strong when first doughed, 
but which fell off in strength comparatively quickly, should evidently 



252 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

be either used in the dough stage or fermented by some rapid method. 
The temperature and atmospheric conditions have also some effect on 
the stiffness of doughs ; this effect though not of wide range is very 
perceptible. It is noticed that sometimes a series of flours give rather 
stiffer doughs at one time than another, while the relative members of 
the series occupy precisely the same positions, one towards the other. 
These variations are not, however, of great extent. 

350. Outline of Method Employed in Viscometric 

Strength Determinations. — The author adopts as his standard 
stiffness for doughs, a dough of such stiffness as allows the piston of the 
viscometer to fall, from mark to mark, in sixty seconds. This dough is 
about the stiffness of that commonly employed for tin bread ; such at 
least is the opinion of several bakers who have seen the instrument. 
Many bakers are in the habit of employing stiffer doughs, while others 
use dough in a slacker condition. The following is an outline of the 
exact process that was employed in doughing and testing flours for 
strength, as given in the subsequent analyses : — One-and-a-half ounces 
of flour are weighed in a counterpoised dish, transferred to a basin, and 
a number of quarts of water added from the specially graduated burette. 
The flour and water are mixed together with a glass rod ; the dough 
and any particles of flour are then removed by means of a spatula, and 
placed in one of Pfleiderer's hand doughing machines for testing 
purposes. The ^machine is fitted with a revolution indicator, and fifty 
revolutions are given to the dough; this is then taken out and placed in 
a small clean tumbler, having its upper edge ground flat ; a ground 
glass plate is taken, a drop of water placed on its under side, and then 
used as a covered for the tumbler. At the end of one hour the dough 
is taken out, very carefully put in the cylinder of the viscometer, and 
then tested by running the piston through, the time being taken in 
seconds. If preferred, the flour and water may be mixed in the machine 
direct, thus saving time. Pfleiderer now specially furnishes for the 
purpose a machine with absolutely water-tight bearings ; one of these 
has been employed by the author in his more recent tests. 

The use of Pfleiderer's machine is not a necessity, but is of service as 
providing a means of doughing with absolutely the same amount of 
kneading in each test. Hand doughing may be employed instead, pro- 
vided it be very carefully and thoroughly done. 

When the character of the flour is known approximately beforehand, 

a quantity of water is taken that, so near as can be judged, shall make 

a dough which runs through in sixty seconds. Having thus made one 

test, if necessary, two more are started two quarts apart, with such 

quantities as shall cause the one dough to be too stiff and the other too 

slack. These are then tested exactly as before, and thereby the strength 

found. Supposing that 68 quarts run through in 37 seconds, and 

70 quarts in 78 seconds, then the following calculation gives the quantity 

equivalent to 60 seconds : — 

78 — 37 

= 11 = number of seconds difference produced by additions 

of a pint. 



STEENGTH OF FLOURS. 253 



37 + (11 x 2) = 59 seconds; therefore 69 quarts would run through 
in 59 seconds, and that quantity is taken as the strength. The principle 
of this will be seen by a little thought — the strength is not given nearer 
than quarts and pints — the difference between the higher and lower 
figures gives the effect produced by two quarts ; each successive pint it 
may be assumed will produce approximately a quarter of this effect, 
therefore if the time equivalent to pint after pint be added, and the 
nearest figure to 60 be taken, then the quantity of water represented 
by this amount will be the quarts per sack according to the definitions 
of standard strength before given. 

351. Results of Viscometric Strength Determinations. — 

The subjoined table gives the strength of various flours, not only at an 
hour, but after standing various other times in dough ; the results of 
various experiments are given ; those in the heavier figures are the 
calculated quarts per sack for 60 seconds. Analyses of these flours are 
given in a subsequent table ; the numbers in both cases correspond. 

DETAILED RESULTS OF EXPERIMENTS, WITH THE VISCOMETER, ON THE 
STRENGTH OF FLOURS. 

No. Names and Description of Flours. 

1 Straight Grade, from No. 2 Calcutta Wheat. 

2 ,, ,, Odessa Wheat. 

3 ,, ,, Saxonska Wheat. 

4 ,, ,, Australian Wheat. 

5 Town Whites. 

6 Town Households. 

7 Taylor's Town Households. 



254 



CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 



1 

No. 
1 


TIME ALLOWED TO REMAIN IN DOUGH. 


IMMEDIATE. 


HALF-HOUk. 


THREE HOURS. 


TWENTY-FOUR HOURS. 




c 


1) 
CO 


a e. 


ui 
•O 

C 
O 
O 
<L> 
CO 


rt " rt 

5, a co 


c 


CO 


t/3 

2 « y 
<y w 


•a 

a 

u 
u 
CO 


i 
1 

i I 

1 

j 

2 

3 


70 
72 

72 


114 
60 

53 


70 

71*5 

72 

74 
""" 


93 
60 

50 
29 


68 
70 

70 
72 
74 


92 
60 

56 

40 
24 


62 

64*5 
66 
68 
72 


77 
60 

49 
3o 
16 


68 
70 
70 

72 


93 
63 
60 

42 






62 
64 

64 
66 
68 


100 
60 

54 
49 
30 


58 
60 
62 
64 


10 
8 
6 

4 


68 

70 

70'5 

72 


90 
66 
60 

45 






62 
65*5 

66 
68 
70 


104 
60 
48 
33 
14 


60 
62 
64 
66 


19 
11 

7 
5 

ii5 
90 
64 

60 

56 


4 


68 
69 

70 


7i 
60 

39 


66 
68 

68 


103 
60 

55 


64 

66 

68 

685 


125 
80 
66 

60 


58 
60 
62 
63 

64 


5 
6 


66 

68 

70 

72'25 

71 


132 
96 
66 

60 
41 






64 
66 

67 

68 


121 
64 
60 

52 


5^ 
58 
60 
61*5 
62 


164 
no 

94 
60 

5i 


68 
70 
72 
72 

74 


116 

76 

63 
60 

38 






64 
66 

66 

68 


120 
60 

53 
47 


56 
58 
59 
60 

62 


125 
63 
60 

55 
40 

60 

35 

21 
18 
11 

8 


7 


64 

66 

665 


160 
76 
60 

:■::::: 


64 
65'5 

66 
68 


132 
60 

47 
25 


62 
62 

64 

66 


64 
60 

37 
30 


55 

56 
58 
60 
62 
64 



STRENGTH OF FLOURS. 



255 



No. 



10 

11 



Names and Descriptions of Flours. 

Porter's Patent Flour, from American Hard Fyfe Wheat. 
Porter's Bakers' Flour, ,, „ ,, 

Hungarian Flour, A A A A A. 
English Wheat Flour. 



TIME ALLOWED TO REMAIN IN DOUGH— ONE HOUR. 




Quarts 






Quarts 




No. 


per 
Sack. 


Seconds. 


No. 


per 
Sack. 


Seconds. 




66 


215 




66 


223 




68 


193 




68 


200 




70 


74 




70 


107 




71 


60 




72 


86 


8 


72 


52 


9 


73 


60 




74 


44 




74 


43 


1 


76 


24 




76 


29 


1 

1 


78 


10 




78 
80 


lb 
12 




74 


255 




58 


183 




76 


170 




60 


120 




78 


60 




62 


82 


10 


8o 


38 


11 


63 


60 




82 


25 




64 


27 




84 


18 




66 


l 9 




86 


10 









256 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 




sTTlb 



fr-iH I 1 I r r I I 



FIG. 52. — DIAGRAM OF STRENGTH RESULTS. 

In this diagram, the results of the Strength tests have been set off as 
a series of curves. On the horizontal lines the numbers representing- 
quarts of water have been set off, and the number of seconds of time 
taken in each viscometer test on the vertical lines. The different series 
of tests on the same flour are distinguished by the letters a, b, c, d> 
being applied respectively to the immediate, half-hour, three hours, and 
twenty-four hours tests. No. 1 a is just a little ahead of No. 1 b, while 
1 d has fallen off 7*5 quarts from the immediate test. No. 3 is a sample 
of Saxonska, and has fallen 5 quarts in three hours, while the Calcutta 
only fell off 2 quarts in the same time ; in twenty-four hours the loss in 
strength is far more than 10 quarts. Considering next the Australian, 
No. 4, its strength, on immediate test, is lower by 1*5 quarts than is 
that of the Saxonska ; but after standing three hours their relative 
strengths are such that the Australian is by 3 quarts the stronger of 
the two, while in twenty-four hours the total falling off is only 6 quarts. 
An extended series of tests has been made on Nos. 8-11 in order to 
show the character of the curves produced in each case. 

It will be noticed that the lines in the diagram vary somewhat in the 
amount of their obliquity ; thus 1 d approaches more nearly to the 
horizontal than does 3 c. This is also frequently noticed in two flours 
doughed under the same conditions ; the conclusion is that the stiffness 
of certain flours is more affected by the addition of the same quantity of 



COMPOSITION OF ROLLER MILLING PRODUCTS. 257 



water than is that of others. As an illustration, compare the curves of 
Nos. 10 and 11 ; the latter is an English wheat flour, and has at 60 
seconds a strength of 63 quarts ; an additional 3 quarts of water 
reduces the viscometer time to 18 seconds. With the Hungarian flour, 
No. 10, the strength at 60 seconds is 78 quarts; an additional 3 quarts 
only reduces the viscometer time to 34 seconds ; while to reduce the 
stiffness of this dough to the same as that of the English wheat flour, 



with an additional 3 quarts of water, requires that an additional 6 
quarts of water must be added. Viscometer tests show, therefore, not 
only the number of quarts of water required by any flour to produce a 
dough of a standard stiffness, but also the sensitiveness of a flour to the 
addition of extra water. Some flours will bear more water being added 
without very greatly lowering their stiffness ; others, by the addition of 
the same extra quantity of water, are reduced almost to a batter. As 
a rule, the weaker flours are also more sensitive to the addition of extra 
water. 
352. Composition of Roller Milling Products.— Now that 

milling has become an art in which the wheat is changed into flour and 
offal, not by one but by many operations, it is a matter, not only of 
interest, but of importance, that it should be known where the con- 
stituents of the wheat go as each successive step in gradual reduction is 
taken, and as the resulting products are gradually purified and 
separated into flours of different qualities and offals. 

Early in 1885 the writer personally collected thirty-four samples 
from a large roller mill recently erected by Mr. J. Harrison Carter, the 
well-known milling engineer, who has taken much interest in the 
progress of these experiments, and has rendered the writer great 
assistance in obtaining the samples and prosecuting his research. He 
has also had the advantage of having as a colleague in this work his 
late assistant Mr. W. Frank Grace, F.C.S. 

The subjoined table gives the moisture, soluble extract, soluble albu- 
minoids, wet and dry gluten, fat, cellulose, ash, and phosphoric acid of 
each sample, and also the colour of the flours. The colours were 
examined before the Standard Scale had attained its final form, so that 
possibly, were the estimations again to be made, there might be some 
slight differences ; such deviations would, however, be only very trifling. 
The results contained in the table are set out graphically in the two- 
page diagram, Kg. 53, inserted on pages 264-5. 

Every care has been taken in ensuring accuracy of the results ; 
where seeming doubtful, duplicate experiments have been performed ; 
these have in some cases led to the making of certain corrections, but 
usually the results have been confirmatory of those first obtained. 

The wheat mixture in use was composed of three parts Winter 
American, one part Spring American, and two parts of California ; it 
weighed 64 lbs. per bushel. 



258 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



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260 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

353. Explanation Of Diagram. — This diagram, Fig. 53, pages 
264 and 265, was arranged and set out by Mr. Zimmer, milling engineer, 
whose services are retained by Mr. J. Harrison Carter. The author 
supplied him with the data contained in the foregoing table, and to- 
Mr. Zimmer belongs the credit of setting out in so clear and admirable 
a manner the tabulated analytical results : the author takes this 
opportunity of expressing his thanks to him for the valuable assistance 
so kindly rendered. 

Each substance analysed is therein represented by a large square :. 
this is in its turn divided by fine ruled lines into 100 smaller squares. 
Each of these small squares may therefore be said to represent 1 per 
cent, of the whole. The different constituents estimated are each 
indicated by particular marking ; thus, water is shewn by horizontal 
lines. All soluble matter is ruled diagonally, with lines descending 
from right to left ; these and the other rulings are explained on the 
diagram itself. In making the analysis, soluble ash was not estimated ; 
but as that body is present in the extract it had to be allowed for ; this, 
was done by assuming that 0'6 per cent, of wheat ash is soluble in 
water : that proportion of the ash is in every case calculated as soluble ;, 
then the soluble extract, less the soluble ash and albuminoids, is assumed 
to consist of dextrin and sugar. It would have been preferable to have 
made direct estimations of the ash in the soluble extract, but this idea 
did not occur until after the completion of the whole series of analyses. 
The spaces left blank represents the difference between the total of 
directly estimated constituents and 100, the difference being made up 
by starch, indeterminate albuminoids, &c. 

In each square the constituents are arranged in the following order :- — 

Water. 

Soluble Albuminoids. Gluten. 

Dextrin and Sugar. 

Soluble Ash. Insoluble Ash. 

Eat. 

Cellulose. 
The general arrangement of the squares will be easily understood by- 
all who are familiar with a milling engineer's " modus operandi." The 
clean wheat is placed in the top left hand corner ; this goes to the first 
break, and is there split up into middlings, tailings, and flour. The 
similar products of each break are arranged in three vertical columns. 
The middlings and semolinas are dressed over Carter's wind purifiers ;; 
the products of the various spouts being shown. No attempt is made 
to illustrate the further reduction and purification of these compounds : 
the flours resulting therefrom, in common with the break flours, produce 
straight grade flour, which again splits up into patent and bakers' 
flours. The composition of the germ and other offals is also illustrated. 

354. Tailings. — Studying first the tailings from each break, the 
moisture contained is somewhat less than that of the wheat ; this is 
doubtless the result of the heat evolved during the milling. The soluble 
extract, soluble albuminoids, ash, phoshoric acid, fat, and cellulose 
gradually increase ; this follows from the fact that more and more of 
the endosperm is being removed at each break, the tailings being 



COMPOSITION OF ROLLER MILLING PRODUCTS. 261 



gradually reduced to simple bran. The gluten at first somewhat 
increases, this is due to the semolina and flour of the earlier breaks 
being made chiefly from the heart of the grain. The portion of 
endosperm nearest the bran contains the most gluten, and so that 
constituent rises, until at the fifth break there is a slight fall ; but from 
the tailings of the sixth and seventh break no gluten is recoverable. 
That, in the sixth break tailings, gluten is nevertheless present is shown 
by the quantity which is obtained from the bran flour. 

355. Break Flours. — Glancing at the break flours, that from the 
first break contains very little gluten, but high quantities of cellulose 
und ash. The second and third break flour is somewhat richer in 
gluten, but is very low in colour. The fourth and fifth break flour is 
low in gluten, but much better in colour. The sixth break flour falls 
off in colour, but is higher in gluten. The seventh break or bran flour 
is high in gluten and fat, low in soluble extract, and specially so in 
colour. 



356. Middlings and Semolinas. — The middlings from the first 

break contain a fair amount of gluten, but the fat and cellulose are very 
high. The first break middlings and flour are treated as offa], and are 
at this stage finally separated from the other products of reduction. 
The granular products of the second and third breaks are separated into 
"coarse semolina" and coarse middlings, the latter being the finer of 
the two. These consist of fragments of the endosperm mixed with 
small pieces of offal, composed principally of broken bran. The pro- 
ducts of the fourth and fifth breaks are also similarly divided. The 
coarse semolinas from the whole four breaks then go together to a set of 
Carter's wind or gravity purifiers, and are separated into three products 
according to their density. The densest of these three is the nearly 
pure broken endosperm ; the middle is a mixture of endosperm and 
branny matter ; while the back spouts yield only very fine branny offal. 
The coarse middlings from the whole four breaks are likewise similarly 
treated over another set of purifiers. 

Considering first the coarse semolinas, that from the second and third 
breaks is lower in gluten than that from the fourth and fifth. It is 
also higher in fat, but lower in cellulose. The bran fragments are 
found more plentifully in the second and third break semolina, while 
the germ finds its way into that of the fourth and fifth breaks. The 
coarse middlings, in each case, are richer in flour-forming constituents, 
consisting of more nearly pure fragments of endosperm ; those from the 
latter pair of breaks being the richer of the two. The next point is 
the nature of the respective products of the separation effected by the 
gravity purifiers on the coarse semolinas. Passing reference has already 
been made to those bodies. The densest bodies, which consequently 
find their way into the front spouts, contain a good proportion of gluten, 
the fat and cellulose being high. The material of the middle spouts 
also contains a considerable quantity of flour forming compounds, but 
no gluten was recoverable from the yield of the back spouts. The 
series of purifiers treating coarse middlings yields from the front spouts 
purified middlings, containing very little matter foreign to flour — the 












262 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

gluten is high, while ash and fat are low — the cellulose is somewhat 
high. The arrangements of the mill permitted of the taking of a sample 
of flour that was being made from these purified middlings only ; its 
analysis is given in the table, but is not shown on the diagram. This 
flour is lower in gluten than the straight grade, but is better coloured 
than even the patent. The middle spouts give a material low in ash y 
but higher in cellulose, than the corresponding yield of the purifiers 
treating coarse semolinas. The back spouts product yields no gluten,, 
but a high proportion of fat, and particularly of cellulose. 

357. Flours. — The whole of the flour from the various breaks, and 
I the reductions of the semolinas (excepting those of the first break), go 

to form the straight grade flour : this constitutes the whole of the 
marketable flour produced by the grain. The water of the straight 
grade flour is almost identical with that of the clean wheat : the soluble 
extract is lower, but the soluble albuminoids run slightly higher. The 
gluten is much higher, amounting to 8*54 against 6*04 per cent. The 
ash and phosphoric acid, 2-05, have decreased considerably ; falling 
from 1-53 and 0'78 to 0'22 and 0*12. The fat and cellulose follow suit, 

falling from 1-582 and I jj'.Jj* (duplicates) to 0-252 and 0-34. The 

colour is 4-59, being exceedingly good for a straight grade flour. This 
straight grade was divided into a small percentage of " Patent," and 
a " Households " or " Bakers' " flour. The patent flour contains rather 
less water than the straight grade ; also less gluten and fat. The 
cellulose of the patent flour is slightly higher than that of the straight 
grade. The households flour is considerably richer in gluten, but in 
other chemical constituents closely resembles the patent. The quantities* 
of fat, ash, phosphoric acid, and cellulose, are in each exceedingly 
small, so that but little difference is observed between either of the 
three flours. The cellulose of flour is in so finely divided a condition 
that the difference in texture of two filter papers might make a per- 
ceptible difference in two cellulose estimations in the same sample. 
There is not the marked difference in quality between the patent and 
households flours observable sometimes : the households has, in fact,, 
not been impoverished in order to produce a quantity of a very high 
class patent flour. In colour, the patent stands at 3 '6 G., the straight 
grade at 4-5 G., and the households at 5-9 G. 

358. Offals : Fine Sharps. — This material, also sometimes 
termed " seconds," looks as good as what one sometimes sees sold as 
flour. It contains a considerable quantity of gluten, 7*0, more- in fact 
than some of the flours : but as might be expected, the fat, ash, and 
cellulose are high. The soluble extract is also very high. 

359. Coarse Sharps, Or Thirds.— These also contain gluten, 
but only a very small amount, 2*64. The soluble extract and albu- 
minoids are very high, so also are the fat and cellulose. 

360. Rolled Sharps. — These are not included in the diagram. 
The soluble extract and albuminoids are even higher than in the 
preceding ; ash, phosphoric acid, and fat, are also high. 



COMPOSITION OF ROLLER MILLING PRODUCTS. 263 

361. Bran. — The bran presents several very interesting matters for 
observation : as might be expected, gluten is absent, and cellulose is 
very high, amounting to over 18*30 of the whole substance. The bran 
also yields more ash and phosphoric acid than any other portion of the 
grain. In the diagram vhe ash is divided, as in the other analyses, into 
a soluble and insoluble portion, calculated on the assumption that 0*6 
per cent, of ash is soluble. With regard to bran, it was thought worth 
while to make an additional estimation of the amount of ash actually 
present in the soluble extract ; the result of this analysis gave 2*61 per 
cent., being considerably lower than the estimate contained in the 
diagram. It does not follow that if the burned ash were treated with 
water that a larger percentage would not be dissolved. The explana- 
tion is that the physical condition of the bran, in broad flakes, is such 
that, whatever soluble matters are locked up within it, they do not 
yield themselves to treatment with water. This is exemplified in the 
case of the soluble extract and albuminoids : compared with the rolled 
sharps the bran yields but 9*33 and 1*20 respectively, against 14*95 
and 3*92 in the sharps. Another sample of the bran was treated with 
water for 24 hours, and then the soluble extract and albuminoids 
determined — the results were 13*1 and 2*2 per cent., still being less than 
in the sharps. These figures afford additional proof of the fact that what- 
ever soluble constituents the bran may possess they do not readily yield 
themselves to water as a solvent : that this is due to the physical con- 
dition is shown by the sharps, which also consist of the integument of 
the grain, yielding so much more soluble matter, the principal 
difference simply being that the latter is much more finely broken. 
The albuminous matter of the bran consists largely of cerealin, with 
which the large cuboidal cells of the inner bran are filled. This body is 
actively diastasic, but is altogether devoid of gluten-like properties. 

362. Fluff. — A sample of this was collected from the pockets in 
Smith's purifiers * the cellulose is higher than that of flour, to which 
the fluff is somewhat similar in appearance. It contains a fair amount 
of gluten, and also of- fat. In appearance this substance looks as 
though it contained a good deal of the cellulose of the endosperm of the 
grain. On consulting figure 40 it will be seen that the starch granules 
are held together in larger cells by walls of cellulose ; these walls most 
probably find their way into the fluff and stive dust. 

363. The Germ. — This most interesting body differs remarkably 
in composition from the other parts of the grain. The percentage of 
contained water is somewhat low, but the soluble extract is remarkably 
high, amounting to just one third of the whole of the body as removed 
in the modern processes of roller milling. Of the soluble extract, 11*76 
per cent, consists of soluble albuminoids as estimated by the albuminoid 
ammonia process. There is no gluten recoverable. The ash and phos- 
phoric acid are high ; the fat also is much higher than in any other part 
of the grain, amounting to 9*076 per cent. Even this amount is less 
than that yielded by some samples examined by the author, from which 
as much as 12 per cent, of fat has been obtained. The cellulose is 
moderately high. 



264 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 




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266 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

Detailed analyses of germ have been made from time to time ; there 
follow results of such analyses made respectively by Tatlock of Glasgow, 
Richardson, and the author. — 





ANALYSES OF GERM. 










Richardson. 


Tatlock. 
Per cent. 




Jago. 




Per cent 


Per cent. 


Per cent. 


Water, 




875 


II- 5 2 




1 3 '23 


Ash, 




5*45 


3-96 


... 


4 '94 


Oil, 




15-61 


5 '40 




12-03 


Soluble in 80 per cent, alcohol 


,26-45 










Insoluble in water, 




1-98 




Dextrin, 


1-24 


Soluble in water, 


2 5*47 


Gum & Sug 


ar, 972 


Maltose, 


5 '54 


Sugar or dextrin, 




18-85 








Non-reducing substance, 




2-94 








Albuminoids, 




3-65 






...... 


Soluble in water, 


4 '44 










Dextrin, 




1 -44 








Albuminoids, 




3-00 








Starch, &c, undetermined, 




9*95 


4076 \ 

5-96/ 




3378 


Cellulose, 




175 




Insoluble albuminoids, 




26-60 Total albds 


., 22-68 Sol. albds., 


^•s 1 




— 




I 


nsol. albds. 


, 1373 




ioo-oo 


IOO'OO 


ioo-oo 



The sample of germ examined by Tatlock was an impure one, the 
analysis having been made in the earlier days of roller milling. That 
examined by the author was from a fine sample of Minnesota wheat. 
The water, ash, and oil were determined by the usual methods. The 
dextrin and maltose were determined by making an estimation of the 
copper oxide reduced from Fehling's solution by the aqueous extract, 
and also taking a polarimetric reading of the solution. The angular 
rotation due to maltose was calculated from the copper oxide precipitate, 
and then the rotation over that amount was calculated as being due to 
dextrin. These quantities are very low, compared with the high soluble 
extract obtained on making a direct estimation of the portion of the 
germ dissolved by water. It is probable that a large portion of the 
sugar of the germ does not reduce Fehling's solution, and so would not 
be estimated in the way just described. A 10 per cent solution of the 
germ in cold water had an angular rotation of + 2*0° in a 20 centimetre 
tube, with sodium light. The starch and cellulose were undetermined, 
the results given being obtained by difference. The total albuminoids 
were determined by a nitrogen combustion ; in order to estimate the 
soluble albuminoids, 600 c.c. of 1 per cent aqueous infusion were 
evaporated to dryness, and a combustion made on the residue. The 
difference between the total and the soluble albuminoids is reckoned as 
insoluble albuminoids. 

As one of the objects of modern milling is to thoroughly remove the 
germ from flour, the actual effect produced by germ, when present, is 
a subject of great importance. An account of some experiments on 
mixtures of germ and flour is given later in this chapter. 

364. Richardson's Analyses of Products of Roller 

Milling 1 . — Clifford Richardson, Chemist to the Department of Agri- 
culture of the United States Government, has made a most important 



COMPOSITION OF ROLLER MILLING PRODUCTS. 267 

and exhaustive series of analyses of products of roller milling. 
Richardson selected samples from three mills ; the first being from 
Messrs. Pillsbury's mill at Minneapolis, where a straight run of spring 
American wheat is used ; the second, Messrs. Herr & Cissel's mill, who 
employ soft winter wheat ; and the third from the mill of Messrs. 
Warder & Barnett, of Ohio, who use all red winter wheat. These 
analyses are of such great value as to warrant their quotation, together 
with the remarks thereon, in full. 



268 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 






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272 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

365. "Interpretation of the Analyses.— The wheat as it 

enters the mill is subjected to a series of operations which removes dirt, 
foreign seed, the fuzz at end of the berry, and a certain portion of the 
outer coats, through the agency of a run of stones and brushes. The 
result of this operation is to lower the amount of inorganic matter or 
ash, and to increase or decrease the other constituents but slightly, the 
albuminoids being a few tenths of a per cent, greater in amount. The 
point from which a convenient start may be made is at the first break. 

" The chop from the first rolls is very marked in its difference in com- 
position from the original wheat. It, of course, has less fibre (cellulose), 
and also it is seen, less ash, oil, and albuminoids ; in fact, it is starchy. 
It contains more water, owing to the fact that its comminution has 
allowed it to absorb the moisture from the air, and in general it will be 
observed that the coarser -or more fibrous a specimen is the less water it 
contains, while the finer material holds more. For example, the per- 
centage of water in several portions of grain are as follows : — 

Per cent. 
Original grain, ... ... ... ... ... 9*66 

Ready for the break, ... ... ... ... 8*23 

Chop from first break, ... ... ... ... 1 2*52 

Fifth break, 7-62 

Bran, 10-91 

" The heat caused by the friction of the process, of course, is an active 
agent ; as may be seen on comparing the original grain and that ready 
for the break. The question of the relation of the various products to 
humidity is, however, considered in greater detail in another portion of 
these remarks. 

" The starchy chop from the first break is carried off to the various 
purifying and grading machines, but for the present it will be left, as it 
is desirable to follow the breaks to the end. 

" The tailings from the first scalper, consisting of the wheat grain split 
open along the crease, which serve to feed the second break after the 
cleaning which they undergo, vary but little from the wheat which goes 
to the first break. There are slight differences which must be attri- 
buted to the difficulty of selecting and preparing for analyses samples 
of the product of the different breaks, the finer chop having a tendency 
to sift out from the lighter bran ; but they are not great enough to 
vitiate the conclusions. In the first break so little is done, except to 
crack open the wheat and clean it for the following rolls, that only a 
small change should be expected. 

" The chop from the second break is more from the centre of the 
wheat grain. It contains less ash, fat, and albuminoids, than any of 
the break products, and includes, as was shown by our preliminary 
investigation, the greater portion of the endosperm. 

" The tailings supplying the third break already show, owing to the 
greater amount of chop produced on the second break, a marked 
increase in those constituents which are peculiar to the outer portions of 
the grain, that is to say, there has been a marked increase in ash, fibre, 
and albuminoids. This increase becomes still more apparent from 
break to break, until the bran alone is left, which contains more ash 



COMPOSITION OF ROLLER MILLING PRODUCTS. 273 

and fibre than any other product of the wheat. The several chops 
increase in a like manner, the last or sixth break chop holding more 
albuminoids than the bran, and even any other of the resulting material. 
This is probably due to the comminution of the bran in the last break, 
and consequently, as will be seen, the middlings from this chop are 
richer in nitrogen than any other, although not the richest in gluten, 
owing to the proportion of bran and germ which they contain. 

" Having followed the grain through the breaks to the bran, the 
products of the purification of the chop remain to be studied. 

" The shorts or branny particles removed from the chop, or from the 
middlings, by aspirators, contain much less fibre and ash than the bran, 
although they are of similar origin, that is to say, from the outer coats 
of the grain. The analyses point to their origin from those portions of 
the coat which contain less ash and fibre. 

"The middlings are graded into five classes, and in their original 
uncleaned state they differ chemically in the fact that from No. 1 to 
No. 5 there is a regular decrease in ash, fibre, and fat, while No. 5 is 
richer in albuminoids than any other. This would be expected from 
our preliminary examination, which showed a decrease in bran from 
beginning to end, and that No. 5 was the purest endosperm. 

" After cleaning, the same relations hold good, but owing to the removal 
of the branny particles there is in all cases a loss of ash constituents 
and fibre. The effect of cleaning is more apparent in Nos. 1 and 2 
where more bran is removed. 

" The reduction of the middlings on smooth rolls changes the com- 
position but slightly, and the flours which originate from this process 
are very similar to the middlings from which they were produced. 
That from the fourth reduction is richer in nitrogen, as would also be 
the case with the fifth, although wants of a specimen prevented analysis. 

"The tailings from the middlings purifiers present the usual charac- 
teristics of bye products, which owe their existence to the outer part of 
the grain, with its high percentages of ash and fibre, and, in this case, 
also of nitrogen. It is remarkable, however, that the tailings marked 
No. 6 contain only one-third as much ash as the others ; but this is 
explained by the fact that they are largely composed of endosperm. 

" The tailings from the different reductions are nearly alike in com- 
position, with two exceptions. Those from the fourth contain little of 
ash fibre and nitrogen. Like No. 6 of the purifier tailings they consist 
largely of endosperm. Those from the second reduction contain much 
germ, and are, therefore, richer in nitrogen than the rest. 

" The repurified middlings, as might be expected, contain much more 
ash, oil, and fibre, than the original, and there is also an increase in 
nitrogen, but not in gluten, owing to the large amount of bran they 
contain. 

" Analyses of three grades of flour as furnished to the market follow. 
From a cursory glance it might be said that the low-grade flour was the 
best, as it contains the most albuminoids, but its weakness is dis- 
covered in the fact that it has only 4 per cent, of gluten. The bakers' 
flour contains more ash, oil, fibre, albuminoids, and gluten, than the 
patent ; but owing to the increased amount of the first three constituents 



i 



274 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

mentioned, it is proportionately lacking in whiteness and lightness. 
The two flours each have their advantageous points. 

" Several other grades of flour, break flour, stone flour, and flours from 
the first, second, and third tailings, are all very similar, and, as far as 
chemical analyses is concerned, good. The preliminary examination 
has, however, shown certain defects in each. The break flour is richer 
in albuminoids and gluten than any other, and if it were pure, and its 
physical condition were good, it would be of value. 

" The roller process is distinguished for the completeness with which 
it removes the germ of the grain during the manufacture of flour by 
flattening and sifting it out. This furnishes the three bye-products 
which are known as first, second, and third germ. They consist of the 
germ of the wheat, mixed with varying proportions of branny and 
starchy matter, the second being the purest. They all contain much ash, 
oil, and nitrogen ; and if allowed to be ground with the flour, blacken 
it by the presence of the oil, and render it very liable to fermentation, 
owing to the peculiar nitrogenous bodies which it carries. 

" The flour from the bran dusters is much like that from the tailings, 
and like the stone stock, from a chemical point of view. This merely 
shows that chemical evidence should not alone be taken into considera- 
tion, for the bran-duster flour is a dirty, lumpy bye-product, while the 
stone stocks are valuable middlings. Analyses of various tailings are 
next in the series, and need no comment. Those of the dust from 
middlings and dust-catchers are rather surprising, in that they both 
contain much gluten, and the first one much fibre ; but this is due to 
their containing both bran and endosperm. 

" To follow the gluten through the process it is necessary to go back to 
the breaks. The amount in the various chops does not vary greatly. 
There is an apparent anomaly, however, in the fifth and sixth breaks, 
where no gluten was found in the feed, but much in the chop. This is 
owing to the fact that the feed has become at this point in the process so 
branny that by the usual method of washing to obtain the gluten it does 
not allow of its uniting in a coherent mass, and separating from the bran. 

" Among the middlings, both uncleaned and clean, the fourth is the 
richest in gluten, and the result of the process of cleaning is to increase 
the amount, although slightly diminishing the nitrogen, which is due to 
the removal of the branny matter, which, though rich in nitrogen, is 
poor in gluten. 

" In the products of the reduction on smooth rolls, the chops from the 
higher middlings are the richest, and if the analyses of the flours are 
complete, No. 4 would probably contain more than the lower numbers. 

"The tailings are, as has been already said, remarkable, not so much 
that No. 1 has no gluten, but that Nos. 2, 3, 4, have 7*62 per cent., and 
No. 6 as much as 14*37 per cent. The regular increase shows that the 
highest number must contain a large portion of endosperm. 

" That this is the case the microscopic examination of the different 
tailings has shown. No. 1 is found to consist almost entirely of the 
outer coating of the grain ; Nos. 2, 3, and 4, of the same, mixed with a 
large proportion of endosperm, which is attached thereto, while in No. 6 it is 
difficult to discover any large amount of anything but flouring material, and 



COMPOSITION OF ROLLER MILLING PRODUCTS. 275 

the small percentage of ash shows also that it cannot contain much bran. 

"In a like manner No. 4 tailings from the reductions has 13-34 per 
cent, of gluten, which is owing to the large proportion of endosperm 
which it contains, and in this case, too, the fact of the presence of so 
much of the interior of the berry is presaged by the low percentage of 
ash. The remaining tailings of this class have little or no gluten, with 
the exception of No. 1, as they contain very little endosperm. 

" In connection with the remaining specimens, the gluten has been 
already mentioned, and the results as a whole warrant the conclusion 
that less of it is wasted in the bye-products than would be imagined. 
For a complete discussion of this point, data, which are not at hand in 
regard to the per cent, of each material produced, are necessary. 

" The products from Virginia wheat, similar to those which have just 
been described, present the same but not as wide variations in the 
breaks and in the flours ; the low grade, instead of containing less 
gluten, has. more than the bakers' or patent. This may be due to the 
greater softness of the wheat, in consequence of which it is less suited 
to the process, a fact which is confirmed to a certain degree by the 
specimens of flour from Ohio wheat, among which the low grade, 
although not exceeding the other brands in the amount of gluten, 
approaches very nearly to them, and it is therefore only reasonable to 
conclude that the spring wheats are particularly suited for roller milling. 

" One of the characteristic features of the roller milling process, as 
has been mentioned, is the removal of the germ of the grain, thus pre- 
venting its injuring the quality of the flour. Among the bye-products 
of the Pillsbury mill are included three separations of germs, known as 
first, second, and third. They are all rich in oil and albuminoids, which 
together form one-half of the substance. The second germ seems to be 
freer from contamination, and was selected for a more detailed ex- 
amination [of which the results are given, together with those of other 
analyses, in a preceding paragraph]. 

" It has been found that the water extract if left in contact with the 
residue of the germ would soon be the cause of a peculiar fermentation. 
This shows the bad effect the presence of this soluble albuminoid would 
have in flour, causing a fermentation or putrefaction which would in- 
jure and discolour it. The oil in the germ is also an additional source 
of trouble, in that it is readily oxidized under certain circumstances 
.and tends to blacken the flour." 

366. Further Examination of Flours Produced during 

Gradual Reduction. — The great importance which attaches to these 
led the author to make a further series of examinations of the flours pro- 
duced at the various breaks and during the reductions of the middlings, 
together with the finished flours, straight grade, bakers', and patent. 
For the series of samples in illustration of this point, the author has to 
thank an important firm of Liverpool millers, whose mill is arranged on 
Simon's system. As being of more immediate importance to the miller 
and baker, the tests have been confined to estimations of moisture, 
gluten, strength, and colour. The wheat mixture consisted of — 

2 Parts Australian. . 

2 ,, Calif ornian. 



276 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



1 Part White Kurrachee. 

2 „ Canadian White. 
2 ,, Chicago Spring. 
2 „ Saxonska. 

1 „ Hard Duluth. 

1 „ Polish Red. 

4 „ Oregon. 

1 „ English. 



18 
In addition to these the author was kindly supplied by Messrs. 
Ure & Sons, of Glasgow, with samples of flour from American Spring 
and Winter Wheats respectively. Descriptions of these, together with 
results of analyses, are also included. 



FLOURS YIELDED BY GRADUAL REDUCTION. 



17 



19 



Description. 



Wheat 

I. Break Flour 

III. ^Breaks Flour 

IV. J 
V. Break Flour 

I. Reduction 
II. Reduction 

j V * > Reduction 

I y | Reduction 

VI. Reduction 
VII. Reduction 
Straight Grade Flour 
Patent Flour . . 
Bakers' Flour 
III. Flour 

Spring American : 

Weakest Break Flour (No. 37 

Fig- 54) 

Strongest Break Flour (No. 38 

Fig. 54) • • 
Strong Flour from last Reduc 
tion of Middlings (No. 39, 
Fig. 54) 

Winter American : 

Weakest Break Flour (No. 2 

Fig. 54) 
Strongest Break Flour (No. 22 

Fig. 54) • • 
Strong Flour from last Reduc 

tion of Middlings (No. 23 

Fig. 54) • • 



a 


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91-0 



FLOURS YIELDED BY GRADUAL REDUCTION. 



277 





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FIG. 54. 

In Fig. 54 the results of the analyses of these flours, together \rith 
those of several others which have been deemed of special interest, are 
set out diagrainmatically. The corresponding numbers, 1-49, across the 



278 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

top and bottom of the diagram refer to the particular flours ; the 
following is an index of these figures : — 

Nos. 1-13. First thirteen flours, given in preceding table of those 
yielded by gradual reduction ; arranged in the same 
order. 
No. 14. Stannards' Crown, see No. 64 in flour tables. 

„ 15. Flour from Old White English Wheat, see No. 14 in 

flour tables. 
„ 16. Flour from Kiln Dried Scotch Wheat, see No. 13 in 

flour tables. 
Nos. 17-19. Taylor's Supers, Whites, and Households. 
No. 20. Straight Grade from very choice Californian Wheat, see 

No. 27 in flour tables. 
Nos. 21-23. Flours from Winter American Wheat, see gradual 
reduction table, 17-19. 
,, 24-25. Flours from Varna W'heat, the former slightly heated in 

hold of vessel, see Nos. 29-30 in flour tables. 
,, 26-27. Flours forwarded from North of Ireland as types of 
flours, respectively fitted and unfitted for breadmaking 
by soda process. 
„ 28-30. Sample of English Seconds, tested immediately on being 
received, and after 2 and 16 days respectively, gentle 
kiln drying, see paragraph 368. 
„ 31-32. Flours from Bombay Wheat, milled respectively dry and 
damped, see Nos. 31-32 in flour tables, and also 
paragraph 367. 
No. 33. Flour from Australian Wheat, see No. 4 in flour tables. 

,, 34. Flour from Odessa Wheat, see No. 2 in flour tables. 

„ 35. Flour from Taganrog Wheat, see No. 28 in flour tables. 

„ 36. Flour from Saxonska Wheat, see No. 3 in flour tables. 

Nos. 37-39. Flours from Spring American Wheat, see gradual 
reduction table, Nos. 14-16. 
„ 40-41. L. C. Porter's Patent and Bakers' Flours, see Nos. 8 
and 9 in flour tables. 
No. 42. Flour from No. 2 Calcutta Wheat, see No. 1 in flour 

tables. 
Nos. 43-45. Best Patent, Second Patent, and Remaining Flour, from 
No. 1, Duluth Spring Wheat, see Nos. 23-25 in flour 
tables. 
No. 46. London Town Households. 

„ 47. Hungarian Patent Flour, see No. 52 in flour tables. 

„ 48. Pillsbury's Straight, see No. 74 in flour tables. 

„ 49. Canadian "Hungarian" Patent Flour, see No. 35 in 

flour tables. 
In the upper part of the diagram the strength in quarts per sack is 
set out, the lowest observed strength, 60, being taken as the limit in 
the direction of weakness ; the higher the line in the case of each 
particular flour, the greater is its strength. These strengths are in 
each case those determined by the use of the strength burette and 
viscometer in the manner already described. 



FLOURS YIELDED BY GRADUAL REDUCTION. 279 

Gluten in percentages occupies the next position ; the diagram pro- 
vides for variations from 7 to 1 7 ; in two instances of abnormally low 
glutens the gluten curve is carried as a dotted line into the next 
division of the diagram. Again, the higher the curve the greater is the 
percentage of gluten. 

Moisture is also set off in percentages, but with this important 
difference : the lowest degree of moisture is placed at the top, and the 
readings go downwards ; therefore, the drier the flour the higher does 
the moisture line reach. 

The colour is set out on the Grey Scale; where the flours are really of 
a yellow tint, or bloom, their hue has been translated into the 
equivalent grey tint. Consequently, the readings of colour must only 
be viewed as showing the degree of intensity of tint, and not its 
character or quality. The colours represented by the lowest numbers 
are placed highest, so that the lower the colour curve the darker is the 
flour. In some few cases colour has not been determined ; this is 
shown by gaps in the colour lines. 

The arrangement of the figures in the moisture and colour divisions 
is reversed, in order that in each instance a rise of the curve shall 
correspond with improvement in quality of the flour, in so far as it is 
affected by that particular constituent or property. 

Considering at this stage those flours taken as illustrations of milling 
by gradual reduction, No. 1, the 1st Break flour, is low in strength (60 
quarts), contains about the average gluten of the series, and is low in 
colour. No. 2 consists of the flour from the 2nd, 3rd, and 4th breaks ; 
this shows but little improvement in strength, rather more in gluten, 
but a decided improvement in colour. No. 3, the 5th Break flour, is 
much stronger, while the gluten is the highest of the series ; this is 
accompanied by a considerable falling off in colour. We have next the 
flours produced by the reduction of the semolinas ; that of the 1st 
reduction is low in strength and gluten but of good colour. The 
2nd reduction produces a flour of improved strength and gluten, with 
but little variation in colour. The joint product of the 3rd, and part 
of the 4th reduction yields a flour, which shows a falling off in strength, 
with a slight increase in gluten. The remainder of the flour from the 
4th reduction, together with that of the 5th, shows an increase in 
both strength and gluten, while the colour somewhat falls off. The 
6th reduction flour is rather higher in strength, while the gluten is 
once more rather less in quantity. The flour from the 7th reduction, 
No. 9, shows an increase in both strength and gluten, while the colour 
becomes slightly darker. We next come to the Straight Grade flour, 
No. 10; comparing this with the Patent, No. 11, and Bakers' flour, 
No. 12, the Straight Grade runs intermediate between the other two in 
strength, gluten, and colour. No. 13, termed " Thirds flour," is 
obtained by again rolling the tailings from the last reduction of midd- 
lings ; this flour it will be noticed is highest in strength, and next to 
the highest in gluten, while the colour is very low. 

Turning next to the series of flours obtained from American winter 
wheats, Nos. 21-23 in diagram, and 17-19 in gradual reduction 
table, the gluten in the weakest Break flour, No. 21, is only 5*3 per 



\ 



280 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

cent., while the colour is very good, and the strength low. No. 22, 
which was the strongest Break flour, shows a slight increase in strength, 
and a considerable increase in gluten : as might be expected the colour 
is slightly lower. Taking next the flour from the last reduction of 
middlings, the strength in this reaches the remarkably high figure of 
91 quarts per sack ; the gluten, however, is absolutely less than that in 
No. 22 ; the colour has slightly fallen off. In these three flours the 
moisture diminishes slightly with the increase of strength. Somewhat 
similar lessons may be learned from the series of flours from American 
spring wheats, No. 37-39 in diagram, and 14-17 in gradual reduction 
table. Again, the weakest Break flour has a comparatively low 
strength, 71 quarts, while the gluten amounts to 12*0 per cent. ; the 
colour is high. The strongest Break flour shows an increase in gluten, 
and a very slight increase in strength ; the colour has fallen off. The 
flour from the last reduction of middlings registers the enormous 
strength of 98 quarts per sack. A dough test, with 88 quarts per 
sack, was mixed with the greatest difficulty, and took 257 seconds to 
run through the viscometer ; the 98 quarts test ran through in 64 
seconds. The gluten of this flour was only 11 '3 per cent., being less 
than in the weakest Break flour ; the colour again descends. In this 
series, as in those from winter wheats, the moisture diminishes with 
the increase of strength. 

367. Damping Wheats. — It is the custom of certain millers to 
add to some of the harder and more flinty wheats, particularly those of 
India, more or less water as a preliminary to milling. The addition of 
such water is popularly supposed to have two effects, the first being a 
softening of the bran, and the second an increased yield of flour. The 
softening of the bran renders it less brittle, and so less is supposed to 
get broken up, and thus into the flour. 

It is essentially a question for the miller, rather than the chemist, to 
decide whether the damping of Indian wheats renders them more 
workable and amenable to milling processes generally. It is quite con- 
ceivable that a " mellow " wheat is more easily converted into flour 
than one which is hard and brittle ; but, against any consideration of 
ease in milling must be set the effect, if any, of damping on the after 
quality of the flour produced. 

It is well known that whereas some millers add but a small quantity 
of water to such wheats as those from India, others use water in 
excessive amounts, undoubtedly with the object of increasing their 
yield of flour by causing it to absorb excessive moisture. A common 
method of damping such wheats is to treat them with a certain pro- 
portion of water ; say, from five to ten per cent, of the weight of 
the wheat. The grain is then allowed to stand about twenty-four 
hours before grinding. During this time a portion of the water will 
be absorbed, and a portion will have evaporated. The opinion of 
many millers is that the absorbed water penetrates no further than the 
bran, except to a very small extent, and therefore that no great increase 
in yield of flour is produced by absorption of water by the endosperm. 

In connection with this subject the author has recently analysed a 
number of samples of Indian and other hard wheats, dry and damped, 



DAMPING WHEATS. 



281 



and also the flours produced therefrom. For the milling data, he is 
indebted to various millers who have been at the pains to specially grind 
these samples of wheat. Subjoined are descriptions, together with the 
analytic results : — 

DRY AND DAMPED WHEATS AND FLOURS. 



Description. 



Flour from No. I White Bom- 
bay Wheat, milled dry 

Flour from Middlings of same 
Wheat, milled dry 

Flour from same wheat, with 
12 per cent, of water added 
24 hours before grinding . . 

Flour from No. 1 White Bom- 
bay Wheat, milled dry 

Flour from same Wheat, with 
7 '8 per cent, of water added 

Wheat, No. 2 Club Calcutta 
cleaned and dry 

Same Wheat, with 4*2 per cent 
of water added 

Wheat, Persian, cleaned and 
dry 

Same Wheat, with 4*2 per cent 
of water added 

Flour from dry Calcutta, F. . 

Flour from damped Calcutta, G 

Flour from dry Persian, H. . 

Flour from damped Persian, I 



s 

3 
'0 


Crude Gluten. 


£ 

s 

"0 


C 1- 

bfiw (J 

ggj; 


1 


>> 
Q 


.2 

X 


I3-20 


26-0 


9'05 


2-9 


6'5 G. 


71-0 


I2-52 


22 -O 


8-13 


27 


5'oG.y. 


70-0 


'374 


27-O 


9-6 


2-9 


9-0 G. 


6 7 '5 


12-51 


23-0 


&3 


2-8 


14-0 G. 


68-o 


U*57 


22 'O 


8-3 


27 


12-oG. 


64-0 


11-58 


I7-0* 


6'3 


2-7 


•• 


•• 


12-51 


15-0* 


57 


2'6 


•• 


■■• 


11-15 


27*0* 


9-6 


2-8 


•• 


•• 


13*30 
n-i6 
11*32 
11-31 
12-03 


17-0* 
20 -o 
22 -o 
29-0 

30-0 


7-24 
7 '4 
8-4 
10-5 
9'8 


2-3 
2-6 
2-6 
2-8 

3-0 


14-0 G. 
14-0 G. 
20*0 G. 
20-0 G. 


75*o 
74-0 
73'o 
73 'o 



*Duplicates of this series of Wet Glutens gave 17-0, 15-0, 26-0, and 17-0 per cent. 

In the case of the first series of samples, A, B, C, the undamped 
wheat was ground on stones, and the flour separated from the middlings, 
which were in their turn reduced to flour, the two being kept separate. 
For the preparation of sample C a quantity of wheat was taken, 
;sufncient to make a sack of flour, and 12 per cent, of water added. 
After standing 24 hours the wheat was milled ; the results quoted, C, 
rare those of the Straight Grade flour. 

The quantity of water added was large ; everyone will be first most 
-interested in the percentage of moisture present in the flour. This has, 
however, only been increased from 13*20 to 13*74 per cent., giving a 
difference of 0*54 per cent. Evidently, then, of the water added to the 
wheat only a minute portion entered the flour. In this particular 
instance the yield of flour, as a result of damping the wheat, was only 
increased to the extent of half per cent, by soaking with 1 2 per cent, of 
water for 24 hours, so far as actual absorption of water by the flour 
was concerned. Of the water added to the wheat but ^V- or ^'l per 
oent., found its way into the flour. 



282 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

The next question is the quality of the flour when produced. In the 
first place analysis shows that the gluten was higher in the damped 
flour ; this was probably due to the mellowing effect produced by the 
absorption of a small quantity of water. The same result would occur 
by letting the dough stand somewhat longer before extracting the 
gluten. It is a well-known fact that from hard wheat flours, such as 
Indian, very little gluten is obtained if the extraction is performed im- 
mediately the flour is wetted. Turning to the strength, the result of 
damping was that the strength fell off from 71 to 67*5 quarts per sack ; 
these measurements were made by the viscometer after the dough had 
stood one hour. This means a loss of strength of 3*5 quarts of 
water per sack, or 81bs. 12oz. of water per 2801bs. of flour, which just- 
equals 3 per cent. The absorption, therefore, by the flour of 0.5 (J) 
per cent, of water, previous to milling, resulted in a diminution of the 
water-absorbing power of the flour, when doughed, of 3 per cent. This 
is due to the fact that the absorbed water deteriorated the strength- 
giving constituents of the flour. Considering next the question of 
colour, the damped wheat flour showed a colour of 9*0 G. against a colour 
of 6 "5 G. in that milled dry. 

The results of analyses of samples A and C are set off in Figure 53 y 
Nos. 31 and 32. 

In passing, it may be mentioned that 1 quart of water per sack equals 
almost exactly 0'9 per cent. (0*89). 

Samples D and E were specially ground by another miller ; the one- 
was milled dry, to the other 7*8 per cent, of water was added. The 
actual quantities were 15^ pints to four bushels of the cleaned wheat,, 
weighing 621bs. per bushel. Again, first considering the water, the^ 
addition of 7*8 per cent, resulted in causing an increase of that present 
in the flour by just 1 per cent., this being about J of that added, or, 
more exactly, 13*6 per cent. In this case the flours, from both tho 
damped and dry wheats, yielded the same percentage of gluten. The 
damped wheat flour was again the weaker of the two, showing a falling 
off of four quarts per sack ; compared with the previous series, the loss- 
in strength is rather more, but does not bear so high a proportion to the- 
amount of water absorbed as in that instance. Here, a gain in moisture 
of 1 per cent, has resulted in a loss of water-absorbing power of 4 quarts 
to the sack, or 3*6 per cent. The colours of the two flours were respec- 
tively 14*0 G. for the dry, and 12-0 G. for that from the damped wheat. 
The former was also decidedly branny. 

The flours and wheats marked F to M were forwarded to the author 
by a third miller, so that the different series represent results gained by 
three mi]lers situated in different parts of the country, and working 
absolutely independently of each other. They thus have the advan- 
tage of representing not only the method of damping employed 
by one man, but those of several. In preparing sample G of 
damped Club Calcutta, a quarter of the wheat was cleaned, and then 
weighed 4801bs. To this, 2 gallons (201bs.) of water were added. After 
24 hours the wheat was re-weighed, and was then found to weigh 
4951bs. ; loss by evaporation, 51bs. The wheat was then once more 
passed through a cleaning machine (nine-inch Victoria, with scourers 



DAMPING WHEATS. 283 



and two strong air blasts). After this, the wheat was ground high on 
stones, and the middlings reduced on rolls, purified and dressed, and 
then mixed so as to produce a straight grade flour. 

The damped Persian was prepared in precisely the same manner, but 
suffered no appreciable loss by evaporation. 

The dry wheats were forwarded to the author in bags, the damped 
samples in tin canisters. The whole were further protected by enclosure 
in sacking. 

In these wheats, the quantity of water added amounted to 4*2 per 
cent., being considerably less than that employed in the previously re- 
corded experiments. Here, determinations have been made of the water 
in the damped wheat itself, as taken immediately before grinding ; that 
is, on being the second time weighed. Taking first the Calcutta wheats, 
as there had been a loss of 51bs. by evaporation, the added water still 
to be accounted for amounted to about 3 per cent. • analysis revealed, 
however, a difference of only 1 per cent. With the Persian wheat ? 
there was no appreciable loss by evaporation, and on analysis the damped 
wheat contained rather over 2 per cent, more moisture than that sent 
dry ■ the wheats were in each case ground prior to estimating moisture. 
In each sample, therefore, there was 2 per cent, of added water which 
was unaccounted for. Circumstances caused some delay between the 
receiving of these wheats and their analysis, the author therefore asked 
the miller to kindly treat fresh lots of wheat and to forward samples. 
These were accordingly treated exactly as before, and sent in the same 
manner. They were dispatched on the one evening and their analysis 
commenced the next morning, consequently no great changes in their 
humidity could have occurred. Determinations of moisture were made, 
both in the whole wheats, and in the meals produced by grinding in a 
hand mill. The whole wheats were kept in the hot-water oven for five 
days. The following are the results : — 



First Samples Second Samples, 

(from previous table). Whole 

Meal. Meal. Wheat. 

Calcutta, dry 11-58 10*33 10-31 

Calcutta, damped 12-51 12-40 13 00 

Persian, dry 11-15 11-44 11-49 

Persian, damped 13'30 13-58 14-60 

Comparing the two sets of samples, when tested as meals, there is a 
very close agreement, except in the case of the dry Calcutta ; the 
discrepancy must be due to either error of analysis, or else actual 
difference in the degree of moisture of the wheat when analysed on the 
two different occasions. The flour from the dry wheat was found to 
contain 11*16 per cent, of water; this closely agrees with what might 
have been expected, if the wheat to start with contained 11*58 per 
cent. On the other hand, the determination of moisture in the meal of 
the second sample closely agrees with that of moisture in the whole 
wheat ; there is therefore very strong collateral evidence in support of 
the correctness of the analysis. Taking the two sets of determinations 
in the second samples, the dry wheat and the meal therefrom agree to 
the second place of decimals ; but, in the damp samples, the meals in 



284 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

each case run considerably lower than the whole wheat estimations. 
This shows that, even in the process of hand grinding, a damped wheat 
loses a considerable quantity of moisture. Tracing the history of the 
4 # 2 per cent, of added water, about 1 per cent, was, in the case of the 
Calcutta, lost by evaporation • no appreciable amount was lost by the 
Persian, and consequently the damped sample of that wheat shows a 
proportionately greater increase of moisture. 

The determinations of gluten in the respective wheats gave some very 
remarkable results. It must be remembered that they stood bottled for 
some days before these estimations were made, consequently any water 
added had full opportunity of effecting any changes within its power. 
In the Calcutta wheats the damping has caused a slight diminution in 
gluten ; this diminution is still more marked in the Persian samples, 
the wet gluten falling off from 27 to 17 per cent. The dry gluten from 
the damped Persian wheat is 2-36 lower than that from the same wheat 
allowed to remain dry. It is curious also to note the remarkably low 
ratio of wet to dry gluten in this latter sample. To make assurance 
doubly sure, duplicate estimations of these glutens were made. The 
lower proportion of gluten in damped Persian wheat is in accordance 
with its greater capacity for absorbing water when damped. The 
changes are not shown to a like extent in the flour, because, although 
the wheats may have absorbed water when damped, but little of this 
water is to be found in the finished flour. 

Turning next to the flours, that from dry Calcutta wheat contained 
11*16 per cent, of water, while the flour from the damped wheat yielded 
on analysis 11*32 per cent. The difference between the two is 0*16 per 
cent., while 4*2 per cent, of water had been added. Of the added water, 
therefore, ^Vj or > more exactly, 3*8 per cent., found its way into the 
flour. The flour from the damped wheat was 1 quart per sack less in 
strength than was that of the wheat milled dry. The damped wheat 
flour gave 8*4 against 6*5 per cent, of gluten yielded by the flour from 
the dry wheat. In colour the two samples were both 14*0 G., there 
being absolutely no appreciable difference between them. 

The examination of the damped Persian wheats showed that they 
absorbed moisture more readily than do Calcutta wheats • the greater 
absorption in this latter instance is also borne out by determinations of 
moisture in the flour. The difference in moisture between the dry and 
damped Persian wheat flours is 0*72 per cent. ; this amounts to an 
absorption of about ^, or, more exactly, 17*1 per cent, of the total water 
added to the wheat. The gluten of the damped wheat flour was 9*8 
against 10*5 per cent, in the flour from the dry wheat. Turning next 
to the strengths, notwithstanding the fact that the damped wheat flour 
contained more moisture and less gluten than did that from the dry 
wheat, yet the strengths were precisely the same. In colour, both the 
Persian wheat flours registered 20 '0 G. ; the two on being tested were 
indistinguishable. 

With regard to these latter four flours, baking tests were made on 
them, with the following results. Water was in each case added in the 
proportion of the number of quarts to the sack given in the previous 
table : — 



DAMPING WHEATS. 



285 





Calcutta. 


Persian. 


Flour 

Water 

Salt 

Yeast 

Sugar 


Dry. 

lbs. oz. 

3 o 

2 O 
O Oj 

o of 

o O^ 


Damped, 
lbs. oz. 

3 o 

o oh, 
o of 
o o\ 


Dry. 
lbs. oz. 

3 o 
i i5f 
o o| 

o of 
o^ 


Damped, 
lbs. oz. 

3 o 

i i si 

o o£ 

o of 
o of 


Dough 

After fermentation 


5 i§ 
5 ii 


5 ii 
5 of 


5 of 
4 15 


5 of 
5 o 


Loss during fermentation . . 


O O 


o 0^ 


o If 


o of j 


Bread 

Loss in oven 


4 9k 
o 8J 


4 9 
o 7 I 


4 * 
o 7 


4 *k 

o 7f 



In each case the dough from dry wheat flour fell off in stiffness more 
during fermentation than did that from the damped wheat. This was 
specially noticeable in the case of the dry Persian wheat flour ; the 
dough, after fermenting some three hours, had become decidedly 
" sloppy." (This falling off in stiffness is not necessarily accompanied 
by loss of weight). When baked, the loaf from the damped wheat flour was 
in each case of better colour ; there was very little difference between 
the heights of the two loaves from the Calcutta flour, but in the case of 
those from the Persian the damped flour yielded a much better risen 
loaf, which, as shown above, was slightly the heavier of the two. In 
flavour, the bread from flours of the damped wheats was in each case 
superior. One observer to whose judgment the loaves were submitted 
(without information as to their respective identities), remarked that the 
dry wheat flour loaves were more " wheaty " in taste. 

Having stated with the utmost care the whole of the details of this 
series of experiments, there now remains to formulate the conclusions to 
be drawn therefrom. In the first place the experiments fairly cover 
the whole of the ground ; the wheats selected have extended from those 
of usual dryness to excessively moist samples of their kind. The 
quantities of water added have varied from the lowest to some of the 
highest percentages commonly used for bona fide damping purposes. 
The milling portion of the experiments have not been made under the 
writer's direct supervision, but he is nevertheless assured that they 
have been carefully and efficiently performed. He takes this opportunity 
of thanking those gentlemen who have devoted so much time and 
trouble to helping him in the attempt to throw some light on this most 
important question. Of the water added to the wheat, a portion, more 
or less, evaporates during the time the grain is standing. The amount 
depends on the degree of humidity of the atmosphere ; as wheat and 
flour both absorb vaporous moisture, and again lose it, with comparative 
readiness. This property undoubtedly accounts for slight discrepancies 
that are at times observed in moisture determinations in wheat. 
Carefully considering the whole of the circumstances affecting this 



286 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

particular series of samples, the writer has arrived at the conclusion 
that any such variations are so slight that they do not in the least affect 
the main question at issue. 

The damped wheat is, before grinding, passed through a scourer ; 
in this machine the greater part of the added moisture is probably 
dissipated. As grinding wheat, whether by stones or rolls, develops 
heat, moisture is lost during this operation, particularly as, with arti- 
ficially damped wheats, the moisture does not apparently penetrate far 
into the endosperm, but mostly lodges within the bran. That the 
moisture of such damped wheats is not held with the tenacity of that of 
wheats in their normal condition is shown by the much greater loss of 
moisture caused by hand-grinding the wheats after damping, as com- 
pared with that of the dry wheats. This point came out strongly in 
the moisture determinations previously given, as being made on the 
whole wheats and the meals therefrom. It is stated, on the authority 
of Mege Mouries, that, on placing wheat in water for 24 hours, the 
moisture penetrates to the heart of the endosperm. Whatever results 
may have been obtained by actually submerging wheat and allowing 
it to soak, no evidence is forthcoming of any but the slightest penetra- 
tion of moisture to the heart of the endosperm as a consequence of the 
ordinary artificial damping of hard wheats as a preliminary to milling. 

Summing up the results of the series of experiments made — 

In artificially damping wheats, but a small proportion of the 
water finds its way into the flour. The actual amount varied 
from 3*8 to 17 '1 per cent, of the total quantity added. 

The addition of water to wheats already containing an 
average quantity of water (in experiment cited, 13 '2 per cent.) 
is decidedly deleterious ; strength and colour are both in- 
juriously affected. 

With wheats in a dry state (11*0 to 11*5 per cent, of water) 
damping in a slight degree does not seriously affect the colour 
or strength of the flour. 

On making baking tests with the flours from such slightly 
damped wheats compared with those of the wheats milled 
dry ; the damped wheat flours fall off less during fermentation, 
yield bread of better colour and flavour, and in practically the 
same quantity. 

The slight damping of the very dry wheats enables the miller 
to produce a better quality of flour. 

Partly from the foregoing experiments, and partly from a study of 

the general properties of wheat and its analogy to other seeds, the 

/conclusion is drawn that the proportion of water absorbed into 

/ the endosperm during the damping of wheat does not increase 

/ with the degree of dryness of the grain. The present experiments 

I do not afford direct proof of this statement, but nevertheless furnish 

important evidence in its favour. In the first place, if the converse of 

this proposition holds good, it would naturally be expected that the 

flour, K, from the driest sample of Indian wheat would have absorbed 

a considerably larger percentage of water, than had the flour C, from 

the dampest sample of Indian wheat. Such is not the case, for the per- 



DAMPING WHEATS. 287 



centage of absorption by the flour, K, is less (3*8) than that by the 
flour, C, (4*1). It may be objected that these flours were produced 
from two different varieties of wheat, and that therefore no comparison 
can be instituted between them. But if a very dry wheat does absorb 
moisture more readily when wetted, than does a sample that is damper 
to start with, it might reasonably be supposed that the absorption 
would at least have been greater, rather than less, with the Calcutta 
sample than that from Bombay, especially as these samples were treated 
in the same manner. Again, if the drier the wheat, the more rapid the 
absorption of moisture, then the damper the wheat, the slower must be 
the absorption of moisture. Taking the flour from damped Calcutta, it 
absorbed but 3*8 per cent, of the added water; then if the wheat had 
only been say 2 per cent, moister to start with, the flour must have 
absorbed considerably less even than 3 "8 per cent, of the water added, 
which would be an infinitesimal proportion. This does not follow from 
a comparison between two different samples, but is a direct deduction 
from most carefully made comparative experiments on one and the same 
wheat. Therefore, the advocates of the hypothesis that water-absorbing 
power diminishes with increased dampness of the original grain, 
must be prepared to admit that if this Calcutta wheat had only been a 
little damper, the water-absorbing power of the endosperm would have 
reached a vanishing point. The view, that the drier the wheat the 
more rapid the absorption of moisture, is at first sight a perfectly 
natural one, as it is a general rule that the drier a hygroscopic substance 
is the more readily does it absorb water, and the endosperm of wheat 
consists principally of starch which is highly hygroscopic. But in the 
case of a wheat grain the endosperm is enclosed within the bran, and 
that altogether alters the conditions. The starch of very dry wheats 
may be more hygroscopie, but the bran is also less permeable to moisture 
as a result of its extreme dryness; and consequently the dry wheat 
grain may offer even greater opposition to the absorption of water than 
would the same wheat when somewhat damper. On high botanical 
authority, this is a property of dry seeds generally, for on placing such 
dry seeds in water, the rate of absorption by the endosperm, within 
certain limits, increases as the absorption itself proceeds. 

In connexion with these experiments, it must on the other hand be 
pointed out that, in the case of the two series of samples milled from 
Bombay wheat, that which in the undamped state produced the drier 
flour, yielded, on damping, a flour which had absorbed a higher pro- 
portion of the added water than had the other. So far, this would 
seem to afford evidence that the drier wheat had more absorbing power ; 
but bearing in mind that the sample was independently treated, and 
also the very cogent reasons adduced in support of the view that the 
proportion of water absorbed does not increase with the dryness of the 
grain, it is far more likely that the difference in the case of samples D 
and E results from E having been differently treated to the other 
damped samples. 

It must be remembered that any differences of opinion which, in the 
absence of absolutely direct proof, may legitimately exist as to whether 
the views above advocated should meet with acceptance, have no con- 



288 



CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 



nection whatever with the statement so conclusively established, namely,, 
that in artificial damping of wheats, but a small proportion of the water 
finds its way into the flour. That fact, in the absence of evidence to 
the contrary, has been indisputably proved, and is perfectly indepen- 
dent of the opinions advanced in the immediately preceding paragraphs. 

368. Artificial Drying of Wheats and Flours. — By means? 

of a series of experiments on flour, Graham very clearly showed the 
advantages derived from gently kiln-drying excessively damp wheats. 
An inferior flour was taken, and one portion heated for some six hours 
to a temperature of 140° F. The dried and undried flours were then 
shaken up with water in the manner previously described for the pur- 
pose of obtaining the soluble extract, except that separate portions of the 
flour and water were allowed to stand for four and eight hours respec- 
tively before filtration. At the end of four hours, the percentage of 
soluble extract, yielded by the undried flour, amounted to 10 '49 per 
cent., while the dried sample gave only 8*7. The difference between 
the two at the end of eight hours is still greater; the undried flour gave 
16*11 per cent, of extract, while the dried sample yielded only 10 "64r 
per cent. Evidently then, this treatment, by partly destroying the 
diastasic power of the albuminoids degraded by moisture, prevents ex- 
cessive diastasis of the starch, on the flour being treated with water. 
The soluble albuminoids, maltose, and dextrin all show a decrease, as 
may readily be seen on consulting the following table : — 





ARTIFICIAL DRYING OF FLOUR (Graham). 


Undried Flour, on Standing 


Dried Flour, on Standing 


Maltose 

Dextrin 

Soluble Albuminoids... 

Total Soluble Extract 


4 hours. 

6-82 
o-43 
3* J 9 


8 hours. 

ii-i 4 

I-2 3 

374 


4 hours. 

4*44 
178 
2-48 


8 hours, 

4 '44 
2-91 
3-29 


io'44 


i6-n 


870 


10-64 



As a result of these experiments, Graham recommended the kiln- 
drying of damp wheat, suggesting that the initial temperature might be 
100° F., increasing slowly to 140° F., at the same time submitting it to 
a current of air, and taking care that the thickness on the kiln floor is 
not too great. (Cantor Lectures, Jour. Soc. Arts, pp. 116-7, Jan. 9, 
1880.) Unfortunately, Graham seems not to have made any gluten 
determinations in these flours. The temperature he recommends 
(140° F. = 60° C), is identical with that at which flour, on being heated 
for several hours, according to Weyl and Bischof, appears to lose the 
faculty of forming gluten. (Jour. Chem. Soc, 1882, p. 537, Abstracts.) 
The author can confirm this statement, having recently repeated their 
experiment, with the same results. If the kiln-drying should destroy, 
or even materially impair, the gluten-forming powers of the flour, this 
would tend to seriously counterbalance the great benefit derived from 
the retardation of diastasis as the result of the application of heat. 



DRYING OF WHEATS AND FLOUES. 



289 



The author recently made a series of experiments on a sample of 
Seconds flour of low quality, stonemilled from English wheats. Imme- 
diately on receiving the sample, its strength, moisture, and colour were 
estimated in the usual manner. A strength determination was also 
made on the dough after standing 24 hours (stability test). The weather 
was intensely cold at the time of making these experiments ; the doughs 
were probably very little above the freezing point, during the time they 
were standing. This is mentioned, because the amount of falling off in 
strength was so much less than that in some previously examined 
samples, the results of which are recorded in paragraph 350, and which 

The flour was next placed above a 



1 e tested during a hot July 



heating furnace, and allowed to remain there for some days ; the tem- 
perature was taken from time to time, by plunging a thermometer in 
the flour, and was found to range between 27° and 30° C. (80 - 6°-86° F.) 
After two days drying a fresh series of determinations were made in the 
flour, and again after sixteen days. The results of the various tests are 
given in the following table : — 

ARTIFICIAL DRYING OF FLOUR. 



Description. 


aJ 

3 
u> 
'3 

3 


Crude Gluten. 


3 


"0 




3 

a oj 


V 

« a 

s a 


1 


u 

Q 


1 


Undried Flour (No. 28, 

Fig. 54) 
Flour after 2 days drying 

(No. 29, Fig. 54) 
Flour after 16 days drying 

No. 30, Fig. 54) 


i3'4 

10-3 

6-5 


29*0 
31'0 

3 2-0 


10-3 

107 
u-6 


2-8 
2-9 
2-8 


12-0 G. 
12-0 G. 
12-0 G. 


67'0 

74'5 

86-o 


65-0 

82"0 



These flours are set out in Figure 54, being bracketed together as 
Nos. 28-30. 

As might be expected, the natural result of drying is to lessen the 
moisture ; this falls in two days from 13 '4 to 10*3 per cent. ; simultane- 
ously -the strength rises 7*5 quarts. A diminution of moisture of 2T 
per cent, corresponds to an evaporation of 2*3 quarts per sack ; but the 
flour shows, as the result of actual trial, that its water-absorbing power 
had increased to a far greater extent. During the sixteen days the 
furnace was not kept continually alight, so that proportionately the 
moisture has not so much diminished as during the first two days. With 
a total diminution of moisture of from 13 "4 to 6*5 per cent., which equals 
6 - 9; the strength had increased by 19 quarts. A diminution in mois- 
ture of 6*9 per cent, is equivalent to loss by evaporation of 7*6 quarts 
per sack, but, as before, the water-absorbing power of the flour has in- 
creased by a much greater quantity. The next point for consideration 
was whether this increase in strength might not be apparent rather 
than real ; and that while the flour would require more water to first 



290 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

convert it into dough, it would fall off to a correspondingly greater 
extent during fermentation. In order to obtain information on this 
point the 24 hours strength tests were made ; they show that the 
original flour fell off during that time 2 quarts, while the dried flour 
lost 4 quarts in strength. Compared with the undried flour, that which 
had been dried until 6 - 9 per cent., or 7*6 quarts per sack of water had 
been evaporated, maintained, after being 24 hours in dough, the advan- 
tage in water-absorbing power to the extent of 17 quarts. In gluten 
the flours show a slight increase as the result of being dried. The three 
samples were exactly alike in colour. These experiments probably 
afford the explanation of that improvement effected in flour by keeping 
for some time. The author was some time ago told by a baker that he 
found, as a result of storing Hungarian flour, that its strength materi- 
ally increased without any sensible diminution in weight. The author 
was, on being told, somewhat sceptical on the point, but his subsequent 
experiments confirm the baker's observations. These experiments show 
that gentle artificial drying of flour increases its water absorb- 
ing capacity to about three times the extent of the water lost 
by evaporation. In all probability, similar drying of damp 
wheats would have a like effect. 

369. General Relationship existing between Strength, 
Gluten, Moisture, and Colour of Flours.— Under this head- 
ing may be considered such flours included in the diagram, Figure 54, 
as have not as yet received specific mention. 

No. 14 is a sample of Stannard's Crown Flour; this is rather a biscuit 
than a bread flour ; it may be noticed that while the strength is very 
low, the gluten is high. This flour is easily hydrated, and forms a very 
ductile dough, specially suited for some varieties of biscuit work. The 
next flour, No. 15, is milled entirely from English wheat : the strength 
and gluten were low, and moisture high ; the colour is fairly good. The 
flour from kiln-dried Scotch wheat is also low in strength and gluten, 
together with high moisture; the colour was very good. It would have 
been interesting to have been able to compare this flour with that made 
from the same wheat undried. Nos. 17-19 are examples of three grades 
of flour from the same miller ; as is usually the case, as the strength and 
gluten increase, the colour decreases. Nos. 24-25 are of interest as 
showing the effect on the quality of the flour of heating in a vessel's 
hold ; the strength and gluten are both diminished thereby. The flours 
33-,36 are marked by their very high percentage of gluten ; notwith- 
standing this, their strength does not rank so high as that of other 
flours, whose percentage of gluten is less : they are respectively, flours 
from Australian, Odessa, Taganrog, and Saxonska wheats. Nos. 40 and 
41 are high in gluten, but still not quite so high as the group just re- 
ferred to ; their strength is however somewhat more. The series 43-45 
are obtained from No. 1, Duluth spring wheat, and serve as an addi- 
tional illustration of different grades of flour, produced during roller 
milling. No. 47 is a Hungarian Patent ; the strength is high ; the 
gluten, medium ; moisture, low ; and colour, good. Pillsbury's Straight 
runs high in strength, rather less gluten than the preceding ; moisture, 
medium. The last flour, No. 49, is of special interest as being the 



EFFECT OF THE GERM ON FLOUR. 291 

of all the flours, which are representative of those that are 
sold as finished products. Nos. 23 and 39 are of course simply inter- 
mediate products of milling. This No. 49 is a Canadian Patent, its 
gluten is medium and its moisture somewhat high ; the colour is fair. 

Reviewing the whole series, the highest strengths are not associated 
with highest glutens, neither are they with lowest moistures ; while the 
low strengths are in some instances found with low, and in others with 
high glutens. Comparing strength with moisture, the dryness of a 
flour does not necessarily correspond with its strength, although in 
many instances a connexion may be observed between them. With one 
and the same flour, increase or decrease of moisture influences th< 
strength to a very marked degree. The colour does not bear a ver 
close relationship to the other properties referred to, because it is so 
largely governed by the methods employed in milling. With flours 
produced at different stages of the same milling process from one wheat 
or wheat mixture, the colour almost always falls off with increase in 
strength and gluten. 

In judging the value of a flour from the analytic data given in this 
diagram, the strength may in the first place be taken as the measure 
of the water required by the flour to produce dough ; it also is the 
principal factor in determining the bread-yielding capacity of the flour. 
Strength tests after standing, or their equivalents, as briefly referred to 
in another part of this work, indicate the degree which the dough will 
fall off during fermentation. The gluten is in the first place a measure of 
the flesh-forming constituents of the flour, and thus partly of its nutri- 
tive value. The quantity and quality of gluten will determine the 
capacity of the flour for retaining the water used in doughing ; and 
also, whether or not the loaf will be well risen and of good pile. For 
instance, although flour, No. 39, will greedily absorb water, yet it would 
not produce so well risen a loaf as No. 38 : this is partly due to its 
containing less gluten, but also to its gluten being of inferior quality. 
The dryness of the flour shows the actual percentage of solid food-stuffs 
which it contains ; and also, as has previously been explained, affords 
indications of its soundness. The colour of the flour, when wetted, is a 
measure of the colour of the bread made therefrom ; apparent discre- 
pancies between the colours of the flour and that of the bread are 
frequently observed, but these are probably due to irregularities in the 
breadmaking process. The same flour will produce bread of many shades 
; of difference in colour, according to whether it be properly or improperly 
manipulated. If his bread be low in colour, the first point on which the 
baker should satisfy himself is whether the fault be inherently due to 
the flour, or to his method of breadmaking. 

370. Effect of the Germ on Flour. — One of the questions 

which for a considerable time has occupied the attention of the milling 
world, is whether or not the removal of the germ affects the flour 
injuriously or otherwise. Among the various authorities on this point, 
Graham, Richardson, and others, are unanimous in expressing a strong 
opinion in favour of its removal. Briefly stated, the reasons thatf* 
render this course advisable are that the presence of the germ discolours 
the flour, and also gives it a decided tendency to become rancid. In • 



Lejr 




/ 



292 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

addition, the germ exerts a marked diastasic action on the imperfectly 
matured starch of slightly unsound flours. On the other hand, the 
advocates for the retention of the germ assert that it renders the flour- 
sweeter, and also causes the bread to have a pleasant moistness on the 
palate. Under any circumstances these results are not likely to be 
attained except by using the flour immediately it is milled ; this is 
frequently impossible, and even then, the baker must be prepared to face 
all those difficulties caused by the presence of active diastasic agents in 
the sponge and dough. Milling experiments, on a large scale, have 
been made on the germy semolina produced during gradual reduction. 
Such semolina, on being reduced on stones, yields a dark coloured 
unsatisfactory flour, which produces a low quality bread. On rolling 
and repurifying these semolinas, the resulting flour is of good colour, 
and yields bread of high quality. So far, these experiments afford 
evidence directly in favour of the removal of the germ. The steady 
demand for roller-made flour demonstrates that the opinion of the 
public, as consumers, is also in favour of its removal. 

In order to test the action of germ on flour, some mixtures were pre- 
pared on Tuesday, February 26th, 1884. It was first necessary to 
decide on a flour which should be entirely degermed. For the purpose, 
the Hungarian flour, from the Economo mills, Trieste, AAAAA., was. 
selected. The germ used was the ordinary flattened germ of roller 
milling processes. There was, consequently, not the same intimate 
admixture which exists when germ and flour are absolutely ground up 
together. One series of samples made up consisted of the following 
mixture : — 

Flour 200-0 grams. 

Germ 15*4 ,, 

"Water ... ... 15*4 ., 

Another set of samples contained : — 

Flour ... ... 200 grams. 

Water 15*4 „ 

These mixtures were put in stoppered bottles and then tied down ; 
the bottles were kept in a cellar, and so throughout the summer were in 
a cool and fairly constant atmosphere. The object of the experiment 
was to determine whether the flour which contained the germ deterio- 
rated more rapidly under the influence of moisture than that which was 
germ free. An extreme case was purposely taken for the first experi- 
ment, because if no decided action had resulted under the most 
unfavourable conditions, it might fairly be assumed that none would 
follow when the circumstances approached more closely to those under 
which flour is stored in practice. On April 1st, two bottles were opened 
and samples tested for acidity and soluble albuminoids. On September 
15th, two other bottles were taken and their contents carefully analysed. 
Both had become mouldy, and had acquired a most disagreeable odour ; 
the odours of the two were, however, of a different character — that of 
the flour and water only was of a musty nature, while the smell of the 
mixture of germ, flour and water was strongly rancid, resembling that 
of rank butter. The mixture containing the germ was far deeper in 



EFFECT OF THE GERM ON FLOUR. 



293 



colour than that of flour and water 
the results of various analyses : — 



only. The subjoined table gives 



No. 



Description of Sample. 



Hungarian Flour 
Same Flour on Sept. 15th. 
Flour & Water, April 1st. 
Flour, Water, and Germ, 

April 1st. 
Flour & Water, Sept. 15th. 
Ditto, calculated to Flour 

without added water 
Flour, Water, and Germ, 

Sept. 15th 

Flour and Germ, mixed 

on Sept. 15th. 
After digestion for 6 hours 

at 28° C. : 
Flour only 
Flour and Water 
Ditto, calculated to Flour 

without added water 
Flour, Water, and Germ 
Flour and Germ, mixed 

on Sept. 15th. 



V 

3 

"5 

s 


Is 

< 




si 

11 

< 


c 
a 
3 


c 

3 
O 
>, 
he 

Q 


.2 

Pi : 


I2'62 


om8 
0-29 

6'22 


4-66 
4-42 


0-93 

I - 02 

l- 5 2 


29*0 
28-0 


9-8 3 
9'33 


2-9 
3 - o 


2I'I5 


0'63 
0'20 


5'5o 


I 94 
3'4& 


I9'5 


6-3 


3*o 


I5-07 


0*2I 


5'92 


3-72 


21*0 


6-78 




27-37 


I- 5 6 

0-27 
076 


9-42 
6-31 

8-64 
12-57 


8-49 
1 -8 1 

1-28 
11-63 


Absent 


Absent 


•• 




o-8i 
1-98 


13*53 
IS'33 


12-52 

1273 






.. 




0-58 


10-31 


1 *93 


•• 


•• 


•• 



The first column to attract the attention of the miller will most likely 
be that headed " Gluten." It will be noticed that during the eight 
months the pure flour has lost a little in gluten, while the soluble albu- 
minoids have slightly increased. In the flour and water the gluten has 
fallen to about T ^- of its original amount ; when wet it was almost semi- 
fluid, and did not rise at all in the aleurometer. In the case, however, 
of the flour, water and germ, the gluten had entirely disappeared. This 
and other experiments show conclusively that the gluten of grain is 
destroyed by the action thereon of the germ in the presence of water. 
As might be expected, the disappearance of gluten is accompanied by a 
rise in the quantity of soluble albuminoids. These were estimated in 
each case by the ammonia process ; the results obtained by that method 
are not to be depended on as absolutely correct ; they must, therefore, 
only be viewed as comparative. The flour and water mixture contained 
less acid when estimated on September 15th than did the flour when 
then examined ; the acid in the mixture containing germ also, had, 
however, risen enormously. The soluble extract in both Nos. 5 and 7 
has increased, but to a greater extent in No. 7. The results are some- 
what complicated in No. 7 by the presence of the germ, because that 
substance also yields soluble extract and albuminoids on analysis. It 
is diflicult to make an exact correction for these on the present analyses, 
but there is no doubt that, making all allowance for the germ, the solu- 
ble albuminoids and extract from the flour itself are considerably in- 
creased by its presence. Samples Nos. 9-13 are ten per cent, solutions 



294 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



of the same mixtures as 2, 5, 7 and 8, maintained at a temperature of 
28° C. (82° F.) for 6 hours and then analysed. The acidity, soluble 
albuminoids and extracts, are in every case higher than before digestion; 
an inspection of the figures will show how the results are affected by the 
presence of water and germ respectively. 

In the estimations made on the flour, water, and germ, on September 
15th, the soluble albuminoids are almost as high as the total soluble 
extract : this applies equally to the sample examined after digestion as 
well as that examined before. The large increase may be due to the 
albuminous bodies being converted into compounds which yield a larger 
proportion of their nitrogen as ammonia, when subjected to distillation 
with alkaline permanganate, than is the case with bodies of the pure 
albumin type. It is also probable, that by a species of fermentation, 
the soluble carbohydrate had been more or less converted into volatile 
bodies. 

These experiments were followed by a series in which the proportions 
of added material were much lower. The same brand of flour was 
selected ; its strength was about 77 quarts per sack. 

The following mixtures were made and bottled — 

F. Flour only. 

F.W. Flour 97*5 parts, water 2-5 parts. 

F.G. Flour 97-5 „ germ 2-5 „ 

F.G.W. Flour 9'5 „ germ 2-5 „ water 2*5 parts. 

These samples were also set aside in a cellar, and allowed to remain 
untouched for twelve months. Their appearance had not considerably 
altered ; the F.W. smelt musty, while the mixtures containing germ 
had developed a rancid odour. The following are results of determina- 
tions made after the twelve months : — 



Description. 


Moisture. 


Crude Gluten. 


Strength 
in Quarts 
per Sack. 


Wet. Dry. 


Ratio. 


F. 

F.W 

F.G 

F.G.W 


n-78 

I3-48 
11-42 
i3'3o 


31*0 
30-0 
33'0 

24-8 


10-59 
970 

10-89 
8-50 


2-9 

3*0 

3"o 

2-9 


78-0 
72'5 

77'5 
71-0 



The water alone had somewhat reduced the percentage of gluten, and 
had also affected the strength to the extent of 6 quarts. The germ 
alone had caused the yield of gluten to be somewhat higher : the same 
effect has been observed in several other similar tests. It is somewhat 
difficult to say from whence the increase is derived, as the germ itself 
yields no gluten. It is probable that the fat of the germ is absorbed 
and retained by the gluten during the washing process ; and also that 
the germ cellulose so closely adheres to the gluten as to render difficult 
their mechanical separation. The germ has not sensibly affected the 
strength. Turning next to the mixture of F., G., and W., the gluten 
is considerably less, thus showing that water and germ, conjointly, are 



EFFECT OF THE GERM ON FLOUR. 295 

capable of inducing greater changes than either taken separately. The 
strength has, in this latter case, diminished to 71 quarts per sack. An 
attempt was made to make colour estimations, but the mixture was not 
sufficiently homogeneous to admit of any readings being taken. In 
experiments such as these the germ is shown to have an injurious 
action, particularly in the presence of water. It must be remembered 
that here a very high-class flour was being used : with a lower quality 
of flour, and the germ ground into it instead of being mixed in the 
above imperfect fashion, the effect of its presence would, without doubt, 
be considerably intensified. 

371. Wheat Blending. — Some of our readers may have expected 
ere this a description of the principles which should govern the miller 
in his selections of wheat for blending purposes ; but, as the end of 
wheat grinding is to produce flour having certain definite characters, it 
has been thought well to postpone the treatment of this question until 
after that of the behaviour of different kinds of flour, during panary 
fermentation, has been fully considered. 

372. Distribution Of Gluten in Wheat.— Considerable interest 
attaches to the relative proportions of gluten in the flours produced 
during the different operations of gradual reduction. Closely connected 
with this question is that of the distribution of gluten in the wheat 
grain. A number of writers on wheat make the statement that gluten 
is found almost, if not quite, exclusively in the inner layer of the bran ; 
and that it constitutes the contents of those cuboidal cells seen so 
prominently in the inner layer of bran when microscopically examined. 
These cells are even now frequently termed "gluten cells" from this 
supposed property. The bran of wheat contains, however, no gluten 
whatever, the whole of that body being derived from the contents of 
the endosperm. Hence it follows that flour contains more gluten than 
does whole wheat meal. The following methods, suggested by Randolph, 
of Philadelphia, may be adopted in order to prove the presence of 
gluten in the endosperm of wheat. 

If whole wheat grains be allowed to soak in water, to which a few 
drops of ether have been added to prevent germination, they will, in a 
few days, become thoroughly softened, and the contents of such a grain 
may then be squeezed out as a white tenacious mass. Examination of 
the remaining bran shows the " gluten cells " undisturbed, closely 
adhering to the cortical protective layers. By now carefully washing 
the white extruded mass, the major part of its starch may be removed ; 
and upon the addition of a drop of iodine solution microscopic examina- 
tion shows numerous networks of fine yellow fibrils, still holding- 
entangled in their meshes many starch granules, coloured blue by the 
iodine. In carefully washed specimens these spongelike networks are 
seen to retain the outline of the central starch-filled cells, and evidently 
constitute the protoplasmic matrix in which the starch granules lay. 
Upon gently tearing such a specimen under a moderate amplification, 
the fibrils will be seen to become longer and thinner, in a manner 
possible only to viscid and tenacious substances — a class represented in 
wheat by gluten alone. 



296 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

An eminently satisfactory proof of the albuminous nature of these 
central networks may be obtained by heating the specimen in the 
solution of acid nitrate of mercury (Millon's reagent), when the fibrils 
wi]l assume the bright pink tint characteristic of albuminoids under 
this treatment. 

Another most satisfactory method of studying the distribution of 
gluten in sections of wheat, is that of removing the starch by diastasis 
effected by malt infusion. If a thin section of a wheat grain be 
momentarily placed in water at 100° C, so as to gelatinise the starch, 
then transferred when cool to filtered malt infusion, and maintained 
from half-an-hour to an hour at a temperature of about 60° C, all the 
starch will be digested away, while the insoluble proteid and other 
constituents will remain entirely unaltered. A section of wheat grain 
thus treated, will exhibit throughout its entire central portion close- 
meshed gluten networks, which become slightly denser towards the 
cortex of the grain. The proteid character of these reticuli is here, as 
in the first method, susceptible of micro-chemical demonstration by 
Millon's reagent. A relatively very faint colouration, indicating the 
presence of albuminoids, is noticeable in the " gluten cells," while the 
gradual condensation of the gluten of the endosperm as the cortex is 
approached is evidenced by a vivid colouration of the fibrils. 

373. Tabulated Results of Flour Analyses.— The following 

tables contain analyses of flour selected from among those made by the 
author during the past two years. Flours have been selected which are 
of interest from one of the following reasons — 1st, their having been 
produced from single wheats ; 2nd, their being well-known brands ; 3rd, 
their representing the flour supply of certain large towns. 



TABULATED RESULTS OF FLOUR ANALYSES. 



297 





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The wheats in Nos. 1-4 were specially ground on stones, and the 
flour produced dressed through No. 9 silks. 

The upper gluten figures in No. 1 were obtained by allowing the 
flour to remain in dough for two hours, before washing out the gluten. 



298 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

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TABULATED RESULTS OP FLOUR ANALYSES. 299 

Flours Nos. 12-16 were milled purely for the ordinary purposes of 
sale, as were also Nos. 19-27, and 35-36. The others were specially 
ground on stones as experimental tests on the respective wheats. Nos. 
19-22 were milled in Glasgow, and Nos. 23-27 in Liverpool. Nos. 28-33 
were all prepared in precisely the same manner as No. 28, hence the 
comparison between them is very instructive. Nos. 29 and 30 show 
strikingly the ill effects on a flour of " heating " in the wheat ; the 
moisture increases, while the strength rapidly falls off. The Indian 
wheat samples are referred to at length in paragraph 367. In 
Nos. 14-16, and 19-22, the glutens were estimated immediately on 
doughing the flours ; in the other analyses, unless specially stated 
otherwise, the doughs were first allowed to stand one hour. Among 
the whole of the flours examined, No. 35, from Canadian Hard Fyfe 
wheat, stands pre-eminent in the matter of strength. The wheat from 
which this sample was made grew in Manitoba, to the north-west of 
Winnipeg, and was forwarded by the Canadian Pacific Railway 
Company, whose efforts to supply the millers and bakers of this country 
with such a magnificent wheat and flour will, as time goes on, amply 
reward their enterprise. 



300 



CHEMISTKY OF WHEAT, FLOUR, AND BREAD. 



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302 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

The Hungarian flour, No. 37, is of the same brand as is No. 10. In 
the first five flours the glutens were estimated immediately, while in 
those following, the doughs were first allowed to stand an hour. Many 
of the earlier analyses were made before the devising of the strength 
testing apparatus, and so do not give that most important factor in 
determining the value of a flour. The flours Nos. 42-44 were made from 
Hard Fyfe wheat, No. 79 in the preceding chapter. Nos. 39-50 are a 
number of well-known brands of American flour. Nos. 52-62 are 
various Hungarian samples ; Nos. 52-56 are different grades of flour 
supplied by the one merchant; so are Nos. 57-59; and again, Nos. 60-62. 
No. 64 is registered as a weak flour, it is, however, scarcely a bread 
flour, being used chiefly as a high-class biscuit flour. 

Nos. 65-67 are flours supplied by one of the largest and best known 
London millers. 

Nos. 68-70 were milled at the same time as Nos. 28-33. 

Nos. 71-73 were obtained from Glasgow, and are representative 
samples of home-milled flours from American wheats : they rival, and 
in some qualities beat, the flours produced from the same class of wheats 
by American millers, and imported into England. 

No. 74 is a sample of Pillsbury's well-known flour, imported into 
London by Messrs. Klein & Sons. 






TABULATED RESULTS OF FLOUR ANALYSES. 



303 






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These flour supplies of large towns call for no very special remarks : 
in addition to the samples here quoted, many of those given in the 
previous tables find their way also into the places included in the 
above list. 



ADVERTISEMENT. 



Henry Simon, 

/billing Engineer, 

20, Mount Street, MANCHESTER. 




The above Cut represents the works for ROLLER MILLS ONLY. 

They are filled with the most carefully selected special 
machinery. Power of production 3 to 4 complete Eoller Mills 
per day. 



BREADMAKING. 305 



CHAPTER XVII. 



BREADMAKING. 



374. Having fully dealt with flour and yeast, there now remain only 
salt and water as essential constituents of bread ; some brief reference 
must be made to these compounds. 

375. Salt, Sodium Chloride, NaCl. — Salt is a white crystalline 
body, about equally soluble in either hot or cold water, and having a 
characteristic saline taste. Salt is used in the making of bread for two 
reasons — first, to give the necessary flavour, without which bread would 
be tasteless and insipid. 

In the second place, salt actively controls some of the chemical 
changes which proceed during fermentation ; thus salt exerts a solvent 
influence on some of the insoluble albuminoids of flour. It further 
checks diastasis, and so retards the conversion of the starch of the flour 
into dextrin and maltose. Salt also checks alcoholic fermentation ; the 
results of careful measurement of this action are given in chapter XL 
The retarding influence of salt also extends to the other ferments, as 
lactic, viscous or ropy ferments, and so tends to prevent injurious fer- 
mentation going on in the dough. 

376. Water. — A great deal of speculation exists as to the action 
on bread of water from different localities. In considering the quality 
of water for dietetic purposes, the chemist, first and foremost, addresses 
himself to the task of determining whether or not the water shows 
evidences of previous sewage contamination. He next ascertains the 
hardness and also the amount of saline matters present. The methods 
he adopts for this purpose vary, but the conclusion at which he seeks to 
arrive is practically the same. It may be safely laid down as a rule 
for the baker that a water which would be rejected, on analysis, as 
unfit for drinking purposes, should also without hesitation be rejected 
by him. Water containing living organisms should in particular be 
carefully avoided, as these might very possibly set up putrefactive fer- 
mentation during panification. 

Among the waters which would be passed by the chemist for 
drinking purposes, there exist, however, considerable differences. Thus 
some are hard, others are extremely soft; salt may be present in 
certain waters, while in others it may be almost absent. The difference 
between hard and soft waters is that the former contain carbonates and 
sulphates of lime or magnesia in solution ; the act of boiling precipitates 
the carbonates as a fur on the vessel used, and so hardness due to the 
carbonates is termed temporary hardness, in distinction from that of 



306 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

the sulphates which, not being removed by boiling, constitutes per- 
manent hardness. 

It has been asserted that processes which in some districts produce 
bread of a certain character fail to produce the same results in other 
localities. Bakers are themselves likely to know better than the writer 
whether such is the fact. The flour and yeast being the same, the 
difference has been ascribed to the water. One notable case in point 
occurred some little time ago, when a London baker is said to have worked 
with Hungarian flour and Vienna assistants, and yet to have found 
himself unable to produce the article known as Vienna bread. The 
fault being ascribed to the water, a Vienna baker, J. F. Behret, asserts 
that it is really due to other causes, and that neither the flour nor the 
water are the culprits. In brewing it is recognised that a soft water 
obtains more extract from the malt than a hard one, but the comparison 
with the case of bread is scarcely fair, because in the wort the liquid is 
filtered off from the " grains," while in bread the whole mass, whether 
soluble or insoluble, goes into the oven together. The general tendencies 
of hard water would be to dissolve less of the albuminoids than would a 
soft water, and consequently the action on the starch would most likely 
be less ; there would therefore be less discolouration of the bread. 
Not only would the quantity of albuminoids dissolved be smaller, but 
with the same quantity in solution their action would be checked by 
the presence of the soluble lime salts. As a consequence, the changes 
which go on during panification proceed more rapidly with soft than 
with hard water. Working in a similar manner, i.e., with the same 
times and temperatures, hard water is not likely to produce as good 
results as soft water at its best. In order to obtain the same results, 
the various steps in the process of fermentation should be somewhat 
modified; thus the bread would probably require to lie somewhat longer 
in the sponge and dough stages, or the temperature employed might be 
somewhat higher. Both colour and flavour of bread depend on fermen- 
tation being allowed to proceed to exactly the right point and no 
further — hence hard water, by altering the length of the fermenting 
process, will affect both these when fermentation is carried out under 
precisely the same conditions with hard water as with soft. Further, as 
the keeping moist of bread depends largely on the degree of change 
produced in the gluten and other constituents, it is quite possible that 
the rate of drying may be effected by the use of hard water. 

The assertion is also frequently made by many English bakers that 
they cannot work successfully with flour barms similar to those used in 
Scotland. The fault here is also commonly ascribed to the water. It 
is far more likely that a want of acquaintance with the practical details 
of the process is the real cause of the failure. Flour barms are suc- 
cessfully employed in France, Scotland, and Ireland : it is therefore 
improbable that any reason exists why they should not succeed in 
England, which lies in the centre of these other three countries. Messrs. 
Stevenson, of Glasgow, now have a bakery on the Scotch system at 
work in London. 

Within the range of ordinary drinking waters the foreign substances 
present may slightly affect the amount of extract obtained from malt in 



BREADMAKING. 307 



mashing, or may slightly retard fermentation ; but beyond this they can 
neither prevent the effectual mashing of malt, nor the subsequent 
alcoholic fermentation of the wort, or of a flour barm. 

377. Objects Of Breadmaking. — The miller's art is directed to 
the task of separating that part of wheat most suitable for human food 
from the bran and other substances whose presence is deemed undesir- 
able. The flour thus produced requires to be submitted to some cooking 
operation before it is fitted for ordinary consumption. Given the flour, 
it is the baker's object to cook it so that the result may be an article 
pleasing to the sight, agreeable to the taste, nutritious, and easy of 
digestion. It is universally admitted that these ends are best accom- 
plished by mixing the flour with water, so as to form a dough ; which 
dough is charged, in some way, with gas, so as to distend it, and then 
baked. The result is a loaf whose interior has a delicate spongy 
structure, which causes good bread to be of all wheat foods the one 
most readily and easily digested when eaten. This charging with gas 
is most commonly effected by fermentation, but other methods are also 
to a limited extent adopted : these will be described in turn. Fermen- 
tation has one great advantage over other breadmaking processes, in 
that it not only produces gas, but also effects other important changes 
in certain of the constituents of flour. 

378. Description of various processes of Breadmaking. — 

The methods employed in the manufacture of bread differ in various 
parts of the country : it will be well to first give accounts of the actual 
processes employed in different localities, and then to describe the 
nature of the chemical changes occuring, and the principles involved. 

379. The Ferment. — Among many bakers the first step in bread- 
making is to make a " ferment ; " this consists of potatoes, boiled and 
mashed with water into a moderately thin liquor. To this the yeast is 
added, and the fermentation allowed to proceed for some time before 
the next step is taken. 

380. The Sponge. — A portion only of the whole of the flour that 
it is intended to convert into bread is taken and made into a slack 
dough with the ferment : this constitutes the " sponge." 

381. The Dough. — The remainder of the flour, together with 
more water, is added to the sponge : this constitutes the " dough." 

Occasionally the whole of the water is used for the ferment ; a 
portion of the flour is added at the sponge stage, and after some time 
the remainder at the dough stage. 

London Practice. 

382. Descriptions follow of the methods in common use in London 
ior making bread, and which represent what is commonly styled 
" London Practice." The first account is by Bennett, and was given in 
a Report to the Secretary of State in 1862, and is quoted by Richardson 
in his recent work " On the Healthy Manufacture of Bread." The 
whole of the following quantities are calculated to a sack of flour. 

383. Bennett's Account. — The ferment is made about twelve 
o'clock in the day in the following manner — nine pounds of potatoes are 



308 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

boiled and mashed in a tub ; this is cooled down with water until at a 
temperature of 80° F. One quart of brewer's yeast is then added, 
together with about two pounds of flour. Fermentation sets in, and 
completes itself in about six hours. At the end of that time the sponge 
is made by adding the ferment to about the quarter of the total flour,, 
and about eight gallons of water : this is kneaded and allowed to fer- 
ment ; this sponge is allowed to rise once, and then fall and rise again : 
on the top of the second rise the dough is made. The sponge takes 
about six or seven hours to undergo the changes mentioned. To the 
finished sponge, the remainder of the flour, about three pounds of salt, 
and another seven or eight gallons of water are added, making altogether 
about sixteen gallons, or 64 quarts to the sack of flour. The dough is 
kneaded, and allowed to stand from one to two hours. It is then scaled 
and moulded, 4 lbs. 6 oz. of dough being taken for the 4 lb. loaf : the 
loaves are then baked from two to three hours. The yield of bread is 
about ninety-one 4 lb. loaves to the sack of flour. 

Bennett's estimate of the time the bread is in the oven is enormous,, 
and so far as the author is aware is far in excess of that now adopted,, 
even in London, where bread is generally kept in the oven longer than 
elsewhere. 

384. Bischof s Methods with Compressed Yeast.— Bis- 

chof, 30, Brooke Street, Holborn, E.C., has recently arranged some 
excellent recipes for making bread, with compressed yeast, according to> 
London practice. ("Encore Yeast Almanack, 1886"). A condensed 
outline of these follows. 

385. Method without Ferment.— Sponge, 7 lbs. best potatoes,, 

boiled, mashed with about 30 quarts of water, and strained into trough. 
This should have a temperature of about 85° F. In a bowl of this 
strained liquor \ lb. of compressed yeast is " dissolved," this is then 
added to the rest of the liquor. From a quarter to a third of the flour 
is next added, and thoroughly mixed. In warm weather, f lb. of salt 
is to be added to sponge. This sponge breaks in about six hours, and 
again rises in another hour. Dough is made by adding another 30- 
quarts of water at 85°, in which either the 3 lbs. of salt, or what remains 
of that quantity after what has been used in the sponge, is dissolved. 
The rest of the flour is added and the dough kneaded. The dough is 
allowed to stand from half-an-hour to an hour, then scaled and moulded. 

386. Method With Ferment.— For the ferment, 7 to 12 lbs. of 
best potatoes are taken, boiled, mashed in a tub with from 2 to 4 quarts 
of water ; when cooled down to 85° F. 2 lbs. of raw flour are added and 
one pint of brewers' yeast. The ferment is allowed to work for about 
five or six hours, and in about seven hours the sponge is set. The 
sponge and dough are made in the same manner as before described. 

Birmingham Practice — 

387. In Birmingham bread is commonly made in the following- 
manner — no ferment is employed; the sponge is made with about 
3 pints of brewers' yeast to the sack of flour, and is allowed to stand 
for about ten hours. The yeast is mostly obtained from small public 



BREADMAKING. 309 



breweries. Salt is used in the proportion of about 2£ lbs. to the sack ; 
but the quantity is increased or diminished according to the strength of 
the flour. In hot weather French and German (compressed) yeasts are 
used either in whole or in part as substitutes for brewers' yeast. When 
•compressed yeast alone is used the sponge is allowed to stand for about 
eight hours. The use of potatoes is almost discontinued in Birmingham, 
as the bakers there are of opinion that they give much trouble without 
any corresponding advantage. 

Manchester Practice — 

388. Some of the Manchester bakers still use a potato ferment, but 
the practice is fast dying out. Compressed yeast is employed almost 
entirely to the exclusion of other kinds. Dutch yeast is most commonly 
preferred, of which 1 lb. is used per sack. One third of the entire water 
is used in the sponge, which is made very tight. The water is used 
either hotter or colder according to the temperature of the atmosphere, 
but no attempt is made to fix the temperature other than by the judg- 
ment of the workman. In two hours the sponge begins to drop : 3 lbs. 
of salt are then dissolved in the remainder of the water, and this, to- 
gether with the remainder of the flour, is mixed in with the sponge in 
order to prepare the dough. In all, about 75 quarts of water are on the 
average used to the sack of flour. The dough after standing one hour 
is weighed off, and is usually baked in tins. The time in the oven is 
one hour. 

Scotch Practice — 

389. This in its turn differs considerably from English modes of 
making bread. For the earlier portion of the following description the 
author is indebted to an article on Scotch Sponging in the " American 
Miller," by Thorns of Alyth. The author applied to Mr. Thorns for 
permission to use his article, and also for data as to Scotch methods of 
•doughing and baking. That gentleman in reply sent a letter which is 
,so valuable that the author thinks it the best plan to quote it in extenso. 

In Scotland, flour barms are largely used, almost to the exclusion of 
•other forms of yeast : the preparation of these barms has already been 
described. The barm constitutes the ferment, and is mixed direct into 
the sponge. Scotch bakers work on either the half or quarter sponge 
system. The following directions for sponging are quoted from Thorns' 
article. 

390. " Half Sponge. — Sponging with either Virgin or Parisian 
barms is identical, whether the sponges are half or quarter. A 2801bs. 
;sack of flour requires over all stages of fermentation from 16 to 18 
gallons of liquor. I assume here that the reader knows all about stir- 
ring a sponge. Half sponge means half of the total liquor in sponge. 
For every five or six parts, whether pints or gallons of liquor in half 
sponge, we give one part of either of these barms. The temperature of 
the sponge liquor, of course, varies with the seasons, ranging from, in 
summer, 76° F. to 84° F., in winter, from 90° F. to 98° F., the sponge 
to rise twice, and be on the second turn within 12 hours. Also, to every 



310 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

gallon of liquor in sponge, when using water of ordinary softness, two 
oz. of salt, and the rest of the salt considered necessary at doughing 
stage. The best flour we find for sponging with these barms is Ameri- 
can North-west ' Spring ' and Russian ' Straight ' grades. Observe, not 
* Bakers,' which means ' straight,' or one-run flour, with the cream, in 
the shape of patent, taken out. The less winter wheat flour used in 
these sponges the better ; it should be used at the dough stage. Few 
varieties of winter wheat flour will rise twice in the sponge and pro- 
duce good bread. Many of them, when sponged without admixture, 
particularly ' patents,' will not rise twice with the purest barm or pressed 
yeast. Limited to winter wheat flour and half-sponging with these 
barms, I would sponge stiff almost half the total flour, and take the 
sponge on the first turn. Sponging with strong glutinous flours, such as 
Hard Spring and Russian, I would use only about one-third of the total 
flour required in all stages ; that is, the half-sponge here referred to is 
only a fair working stiffness. 

391. "Quarter Sponge. — This system is found most convenient 
where machinery is used (the half-sponging where hand-labour is em- 
ployed for sponging and doughing), and means J of the total liquor for 
a known quantity of flour in the first stage, instead of ^ as in half- 
sponging. Quarter-sponging is done in tubs. Sponge for one sack of 
flour requires a tub of 50 gallons capacity. Say we wish quarter-sponge 
ready for doughing at 4 a.m. to-morrow, then at 2 p.m. to-day we take 
— for making about one sack of flour into bread — 3 gallons water, 1 J or 
1 J gallons barm, and six oz. salt, and mix these with the necessary flour 
into a sponge as stiff as batch dough. In 12 hours, or 2 a.m. to-morrow, 
the sponge will be turned, the first time J an inch, then we break in or 
up with machine or hands the quarter with 12 gallons more water,, 
li lbs. or 1J lbs. more salt, and add enough flour to form a very weak 
sponge. This will rise again in the tub and be on the turn in about 2 
hours, or 4 a.m., when the remainder of the salt necessary is dissolved 
in \ gallon water, and dough made. Many, and especially in cold 
weather, do not dissolve the salt in water, but simply sprinkle the salt 
over the sponge in the machine or trough. It will be observed that in 
neither the half nor quarter sponges is there ferment or potatoes used. 
The barm is the ferment, and is added direct to the sponge. For regu- 
lating fermentation in warm weather, in addition to colder water, it is 
advisable to reduce the quantity of barm or yeast, and in cold weather 
to increase it." 

392. Doughing and Baking. — Here follows Mr. Thorns' letter — 
" My article in the " American Miller " on " Flour Barms and Sponging " 
leaves off with the sponges ready at 4-0 a.m. Let us suppose the 
sponges "broken in"- — the technical term — with the necessary salt and 
water, we then mix in the flour. Yes I but what flour % Spring 
American is supposed to be used in sponges, and what we will use in 
dough will depend on the price for the flour, the price for bread, and 
whether our bread is to be crusty as in England, or close packed, high 
volumed, and silky skinned as in Scotland. In England I might use 
all Winter American flour in dough, here not more than half Winter— 



BREADMAKING. 311 



sound red. What home grist we have goes into the dough, together 
with part Spring flour. Indian wheat is going largely into English 
grist, but I would prefer the Indian in sponge. I doubt the dough 
stage being long enough to allow the hard gluten of Indian wheat time 
to sufficiently hydrate and soften [peptonise] ; without which the bread 
would be harsh, low, dry soon, &c, &c. Germany, Denmark, and 
Belgium send us flour largely, but of late I find the flours of the two 
former countries of little use for biscuits and loaf bread, owing to the 
large admixture of Indian wheats. 

"The doughs, of whatever flours composed, will be made by 4.30 or 
4.40 a.m., and are allowed to lie for £ hour, then turned, dry dusted, 
and kneaded from one end of the trough to the other and back again ; 
and in another | hour or so, or about 6.0 a.m. they are thrown out and 
scaled off. Where kneading machines are employed the dough should 
have more mixing, in order to knock out proof before throwing or 
turning out. How do you know when it is ready to throw out and 
scale off 1 We judge only by feel and smell. The dough should feel 
tight, lively, and resistant, tear easily ; and the rent, on the head being 
held down and a deep inspiration taken through the nose, should show 
carbon dioxide in volume nearly suffocating, accompanied by a slightly 
vinous odour. 

" If scaling off begins at 6.0 a.m., moulding the loaves may begin at 
about 6.30 or 6.45. This refers to medium slack doughs for close 
packed bread ; stiff doughs require longer. After moulding, the medium 
slack loaves are allowed from 15 to 30 minutes to prove in the boxes, 
and then run into the oven. Stiff dough, again, requires longer proof ; 
and, except in summer, the boxes holding the moulded loaves are slightly 
heated. 

" The time in oven for 4 lb. close-packed square loaves is two hours, 
and the best baking temperature 400° F., while the bread is baking. 
For 2 lb. square loaves, the same temperature, time, 1J hours; these 
data refer to both steam and Glasgow ovens coke heated inside. A 
higher temperature and shorter time we find carbonises the top and 
bottom crusts, while the crumb in the heart of the loaf is more or less 
raw. Crusty loaves, 4 lbs., slightly packed, temperature about the 
same or a little less, 380° to 400° F., and time, 1 J hours ; 2 lb. crusty 
loaves, same temperature, time, 1 hour. These are not the shortest 
times in which the various breads can be baked, only what experience 
has shown me to be the best.' The baking heats refer to the time while 
the breads are in the oven. If the fires are lighted at 4.0 a.m., it will, 
of course, be necessary to heat the ovens higher than that ; how much 
higher will depend on the heat of the ovens before lighting the fires. 
On Mondays we go higher than on other days ; the steam ovens we 
heat up to 480° F. ; the ovens heated with coke or coal inside we heat 
up to 550° F. By the time the batches are ready to go in they will 
have cooled down to 420-30° F., and by the time the batches are actually 
in they will show a temperature of 410-15° F." 

Review op Panary Fermentation — 

393. It is proposed in the succeeding paragraphs to consider the 



No. i. 


No. 2. 


76-40 


75-20 


14-91 


15-58 


2-17 


3-60 


2-34 


1-29 


0-15 


111 


0-29 


0-31 


1-70 


1-99 


0-99 


1-03 


1-00 


0-90 



312 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

nature of the chemical changes which occur during bread or panary 
(from panis, bread) fermentation. Suggestions will also be made as to 
possible improvements in methods of carrying out the various processes, 
with the hope that they may lead to the avoidance of those causes which 
result in the production of bad or inferior bread. 

394. The Ferment.— Potatoes, termed by the baker " fruit," con- 
stitute the principal ingredient of the ferment ; their composition is 
indicated in the following analyses. No. 1 was grown with mineral 
manure, No. 2 with a rich nitrogenous manure : — 

Water ... 

Starch ... 

Albuminoids 

Dextrin 

Sugar 

Fat 

Extractive Matter 

Cellulose 

Ash 

Roughly speaking, a potato contains three quarters of its weight of 
water, and about 1 5 per cent, of starch ; the remainder being made up of 
small percentages of albuminoids, dextrin, and sugar and other substances. 
On being boiled, the starch is gelatinised, and on mashing the potatoes, 
together with the liquor in which they have been boiled, a starch paste 
is formed, containing also considerable quantities of dextrin and sugar, 
and what is of great importance, soluble nitrogenous compounds. Yeast 
on being sown in this medium sets up an active fermentation, largely 
due to the sugar already present, together with the strong nitrogenous 
stimulant. In chapter XI., it has been demonstrated that the fermen- 
tation is almost as active in the filtered potato water as in the mash. 
It must also not be forgotten that yeast alone is incapable of inducing 
diastasis in starch paste. Consequently, any unaltered starch suffers 
little change in a ferment containing only boiled potatoes and yeast. 
But raw flour being also commonly added, the yeast induces a change 
in the flour albuminoids in virtue of which they become somewhat active 
hydrolysing agents, and so the potato-starch is indirectly converted in 
part into sugar. The yeast, when sown in a ferment, multiplies by 
growth, and thus a relatively smaller quantity of yeast is enabled to do 
the after work. A large proportion of the starch of the potato still 
remains unchanged at the close of the fermentation of the ferment ; so 
also, the nitrogenous matter of the potato in great part remains. When 
the ferment is added to the sponge, the smaller quantity of yeast not 
only does more work because of its having had the opportunity of growth 
and reproduction in the ferment, but also because the nitrogenous matter 
of the potato still acts as a yeast stimulant in the sponge. The active 
effect of potato water alone, shows that this stimulating action of the 
ferment on yeast must not be entirely ascribed to the starch present. 
From the active stimulating nature of the nitrogenous matter of potatoes 
on yeast, it seems probable that that matter consists of nitrogen in some 
other form than albuminous compounds. Summing up these changes 



: 



BREADMAKING. 313 



into one sentence, in the ferment, the yeast acts on the soluble 
albuminoids of the flour and enables them to effect, to a 
limited extent, diastasis of the starch : this results in the pro- 
duction of a saccharine medium in which the yeast grows and 
reproduces ; further, the soluble nitrogenous matter of the 
potato acts as an energetic yeast stimulant. 

It is essential that the potatoes used in the ferment be sound : they 
,-should first of all be washed absolutely clean. A common practice is to 
^place them in a pail or tub, with water, and scrub them with an ordi- 
nary bass broom ; this treatment is inefficient, as potatoes served in this 
way still retain a considerable amount of dirt. The potatoes are then 
boiled in their jackets, and afterwards rubbed through a sieve in order 
i;o separate the skins. By far the best plan to clean potatoes is by 
means of a machine; one patented and sold by Hancock, of Birmingham, 
answers well for all practical purposes. The machine consists essentially 
•of an outer tub, in which is fixed a vertical revolving brush : the 
potatoes are put in, and about two minutes turning the brush cleans 
them most effectually. The dirt is removed, and also a good deal of the 
outer skin, while the interior of the potato remains intact. Treated in 
i;his manner the potatoes have only just the slightest film of skin to be 
removed, after boiling, by means of the sieve. In the next place, the 
^pan, or other vessel used for boiling the potatoes, should be kept clean ; 
i;his is only done by its being washed, drained, and wiped dry every day. 
Not only the potatoes, but the water in which they are boiled, should 
be quite clean enough, if need be, to go into the bread. At present, 
many bakers steam their potatoes in preference to boiling : this modifi- 
cation is cleanly and convenient. The potatoes are placed in a metal 
work cage, which in its turn is placed in a box arrangement, through 
which steam is conducted from a boiler : when sufficiently cooked, the 
cage, together with the potatoes, is lifted out, and its contents poured 
on to a sieve. The ferment should be rapidly cooled to the pitching 
temperature of about 80° F. in summer, and 85° in winter : in summer 
it is very important that the baker should throughout conduct his 
-fermentation at as low a temperature as possible. During the time 
that a ferment is working the temperature should be kept even : for 
this purpose select a place in the bakehouse free from draughts or 
-excessive heats. 

395. Panary Fermentation. — The consideration of the division 
•of this process into sponging and doughing may be postponed until after 
a, study of the nature of the changes occurring during panification as a 
whole. Yeast, flour, and water, at a suitable temperature, on being 
mixed so as to form a dough, immediately begin to react on each other. 
"The flour, it must be remembered, contains sugar, starch, and both 
soluble and insoluble albuminoids. The yeast consists essentially of 
saccliaromyces ; but bacterial life is also present in greater or less 
quantity. The yeast rapidly sets up alcoholic fermentation, thus 
causing the decomposition of the sugar into alcohol and carbon dioxide 
gas ; the latter is retained within the dough and causes its distension. 
Functioning in dough, little or no reproduction of the yeast occurs ; 
after a time the yeast cells disappear through the degradation and 



314 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

rupture of their walls. In addition, the yeast attacks the albuminoids 
present, effecting changes in them which are similar to, if not identical 
with, the earlier processes of digestion. Albumin and its congeners are, 
in fact, more or less peptonised. The gluten, from being hard and 
india-rubber like, becomes softer, and within certain limits more elastic ; 
but if fermentation be allowed to proceed too far, the gluten softens still 
further, and its peculiar elasticity in great part disappears. It is. 
uncertain to what extent these changes in the gluten are due to the 
specific action of yeast, as they also occur, although more slowly, in flour 
which has simply been mixed with water. It has been already ex- 
plained that under the action of yeast the albuminous bodies of flour 
acquire the power of effecting the diastasis of starch ; this compound is 
consequently to some extent converted into dextrin and maltose during: 
panification. The amount of starch so hydrolysed depends largely on 
the soundness of the flour. When potatoes are used, whether as a 
ferment or as a direct addition to the flour, they furnish soluble starch, 
and also act as a nitrogenous yeast stimulant. While the yeast effects 
important changes in the albuminous compounds of flour, experiments, 
made and described in chapter XI. show that little or no gas is evolved 
as a consequence of such changes. The gas produced in dough during- 
breadmaking is the result of normal alcoholic fermentation of sugar by 
the yeast. Summing up the changes produced in panification — 
they are alcoholic fermentation of the sugar, softening an& 
partial peptonising of the albuminoids, and a limited diastasis 
of the starch by the albuminoids so changed. 

So much for the action of yeast on dough. The next point of im- 
portance is the effect produced by such other organisms as may be 
present. The principal one of these is the lactic bacillus; under its- 
influence the sugar of the dough is converted into lactic acid. Either 
the organism itself, or the acid produced by its action on sugar, has a 
softening and dissolving effect upon gluten. Opinions differ as to the 
desirability, or otherwise, of the presence of lactic ferments in yeasts 
used for breadmaking. It has already been explained that their being^ 
found in any but the smallest quantity in brewers' or compressed yeasts 
is an unfavourable sign, as they show that due care has not been taken 
in the manufacture of the yeast ; for that reason their presence is 
deemed unfavourable. In Scotch flour barms the presence of lactic 
ferments in not too great amount is deliberately encouraged ; experience 
having shown that if the barms be brewed so as to exclude these 
organisms such good bread is not produced. In Scotch breadmaking- 
very hard and stable flours are used ; the lactic ferment does good 
service in softening the gluten. It is possible also that during the long 
period of sponging and doughing, the changes induced by the lactic 
ferment may cause the evolution of gas ; experiments having shown 
that a malt wort which, on careful microscopic observation, showed no- 
signs of the presence of yeast cells, but was swarming with bacteria, yet' 
gave off a considerable quantity of gas on being placed in the yeast 
apparatus. (See paragraph 289, chapter XI.) It must be remembered 
that the soupfon of slight buttermilk flavour is a valued characteristic? 
of Scotch bread. In breadmaking, as conducted by most English pro- 






BREADMAKING. 315 



cesses, particularly with soft flours having but little stability, there- 
seems no useful function which the lactic ferment can perform ; its 
absence is therefore rather to be desired than its presence. A yeast 
may contain other organisms in addition to those just mentioned ; these 
are capable of inducing changes of a far more serious nature than does 
the lactic ferment. Among these there are the organisms which cause 
butyric and putrefactive fermentation. That bane of the baker, sour 
bread, is commonly ascribed to the action of either lactic or acetic fer- 
mentation ; it is, however, far more probable that this unwelcome 
change is due to butyric fermentation ; since the odour of a sour loaf 
is very different from that of either the vinegar-like smell of acetic acid 
or the buttermilk odour of lactic acid. The souring takes place more 
usually in the bread rather than in the dough. 

In order to produce a healthy fermentation in dough, healthy yeast is 
of vital importance : purity from foreign organisms is desirable (saving, 
perhaps, a small proportion of lactic ferment in flour barms), but above 
all the yeast itself must be active and in good condition. Given a 
yeast, which contains a certain percentage of foreign ferments, those 
ferments will be held in abeyance while the yeast itself is energetic and 
healthy. Bakers are often puzzled by microscopic observations of yeast; 
they And that, of two yeasts, one produces sour, and the other a 
good bread, and yet that the two contain about the same quantities of 
disease ferments. They are consequently very apt to despise any con- 
clusions they may have drawn from microscopic observations ; but the 
difference in such cases lies in the yeast itself, the one will be healthy, 
the other weak and languid. Quoting again from previously described 
experiments, in the same sample of wort, divided into two portions, 
the one only of which was sown with yeast, and both equally exposed 
to the air, it was found that in the presence of yeast life, bacteria refused 
to develop, while in its absence they reproduced with enormous rapidity. 
In the same way the healthy yeast suspends the developments of bacteria 
in dough, while the yeast being weak and almost inactive, bacterial life 
flourishes apace. Examination would reveal that in most cases of 
unhealthy panary fermentation the fault is as much due to the yeast 
itself as to the abnormal presence of foreign ferments. 

396. Sponging and Doughing.— This division of the process of 
panary fermentation into two distinct steps is of extreme interest. 
The origin, and reasons which led to the adoption, of this mode of 
procedure, are to a great extent lost in obscurity ; but they have, never- 
theless, a most important scientific justification. The reader will by 
this time be familiar with the division of flours into strong and weak 
varieties. The strength tests given in a preceding chapter show, not 
merely that one flour absorbs more water than another to form a dough 
of standard stiffness, but also that some flours fall off far more rapidly in 
strength than do others when kept in the condition of dough. There are 
therefore two distinct properties here to be considered in relation to flour, 
the absolute quantity of water it absorbs, and also the rate at which 
weakening goes on during panification. Still, defining " Strength " as 
the measure of actual water-absorbing power, the relative capacity 
of resistance of flours, to a falling off in strength during fer- 



316 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

mentation, may appropriately be termed their " Stability." As 
a rule, the strong flours are also the more stable, but this does not 
necessarily hold good in all cases. It has been already explained that, 
for the production of the best bread, fermentation should be allowed to 
proceed sufficiently far to soften and mellow the gluten, but no further. 
At stages, either earlier or later than this, the bread will lack both in 
appearance and flavour. It is therefore necessary to so regulate fer- 
mentation as to stop at precisely this point : unfortunately no exact 
means are at present known whereby it can be determined with 
precision. The more stable a flour is the longer it requires to be 
fermented before this point is reached, hence where flours of different 
qualities are being used the more stable should be set fermenting earlier 
than the others. In this lies the reason for using some flours at the 
sponge, and others at the dough stage. Flours from hard wheats, such 
as Spring American or Russian, should be used in the sponge ; and 
American Winter, or English wheaten flours in the dough. Working 
with stable flours in the sponge, experience has shown, according at 
least to the London practice, that the best results are obtained by 
allowing the sponge to rise and fall once, and then to rise again. The 
time taken for this rising and falling is found to agree with that 
necessary for the sufficient mellowing of the gluten. This empirical 
test, which is the result of careful watching and experience, is at present 
the baker's principal guide in determining the progress of fermentation. 
It affords evidence of the degree of rapidity with which gas is being 
evolved, and indirectly of the extent to which the other chemical 
changes have proceeded. It seems probable that by measuring the 
stability of flours, by means of the viscometer, it would be possible to 
arrange them in the order of the time they would require to be in fer- 
mentation, and thus to afford the baker a guide in selecting his flours, 
and determining the relative durations of his sponge and dough stages. 
It is possible that the same instrument might be so adapted as to enable 
the stiffness of a dough to be measured by means of it from time to 
time during fermentation. This, coupled with a table based on experi- 
mental comparisons of determinations with the instrument, and actual 
baking tests, may at some time in the future enable the baker, who so 
wishes, to estimate with rapidity and accuracy the point at which 
fermentation will have attained maturity. The author hopes at some 
time in the future to publish the results of experiments made in this 
direction. 

397. Variety and Quantity of Yeast used. — The variety 

of yeast employed produces a marked effect on the character of the 
resultant bread. Good brewers' yeast is almost universally admitted to 
induce a characteristic sweet or " nutty " flavour, hence it is largely 
used in the manufacture of so called farmhouse bread. Colour in this 
variety of bread is secondary to sweetness of flavour. While brewers' 
yeast has a somewhat energetic diastasic action on the albuminoids and 
starch of dough, its fermentative power is comparatively low in that 
medium. Undoubtedly, one of the reasons which has led to the com- 
paratively extensive use of potatoes in breadmaking is their stimulant 
action on the gas-producing power of brewers' yeast in dough. 



BREADMAKING. 31 7 



Continental compressed yeasts, on the other hand, are marked by 
their rapid power of inducing alcoholic fermentation in dough : experi- 
ence indicates that neither potato nor flour ferments are necessary when 
working with these yeasts, although those bakers who have been in the 
habit of using potatoes will probably, by preference, for some time at 
least, continue the practice. But with the absence of such pressing 
necessity, and with the knowledge that in some towns, specially noted 
for the high class of their bread, the habit of using potato ferments is 
rapidly becoming extinct, bakers are likely, in the future, to give up 
the use of such ferments. 

Motives of economy on the part of the bakers, and competition on the 
side of the yeast merchants, both lead to a certain rivalry among the 
latter as to whose yeast is able, weight for weight, to adequately ferment 
the greatest quantity of flour. Now, while it is important that the 
baker should know with accuracy the relative strengths of different 
brands of yeast, it is nevertheless not wise to be too sparing in the 
quantity employed to a sack of flour. Although half-a-pound of yeast 
may be sufficient to ferment a sack of flour, yet three-quarters will do 
it much better, and probably with greater economy in the long run. 
First, select the strongest and purest yeast you can get for the money, 
and then don't be afraid to use sufficient of it. This advice should 
have especial weight in the south of England, where soft, weak flours, 
having comparatively little stability, are so largely employed. Flours of 
this kind will not bear being kept so long in the sponge and dough 
stage as is necessary to ferment them with a very small quantity of 
yeast : they, if so treated, produce sodden, heavy, and sometimes sour 
loaves ; while any saving in yeast is more than compensated by a less 
yield of bread. 

398. Management of Sponging and Doughing. — In order 

to ensure success in the manufacture of bread, sound materials are the 
first requisite : after that the most important in this, like all other 
operations in which fermentation employs an important part, is the 
proper regulation of temperature. The yeast should always be stored 
where it will get neither too hot nor too cold ; for extremes of tempera- 
ture in either direction weaken the action of yeast. Brewers' yeast in 
particular suffers from this in summer weather ; and so, many bakers 
who use it in the winter, change over to compressed yeast in the 
summer. In summer time the compressed yeasts are when fresh more 
active than in winter : in proof of this, compare the results of tests 
made and given in chapter XII. In winter the strength of the yeast 
may be increased by allowing it to stand for a time in water at 85° F. 
before being used. A still better plan is to stir a handful of raw flour 
and a small quantity of sugar into a bowl of water and then add the 
yeast ; let this stand for about an hour, gently stirring now and then in 
order to aerate the liquid. Such treatment refreshes and invigorates 
the yeast, and so enables it to afterwards work more actively. Both 
sponge and dough should be so managed as to keep the temperature as 
nearly constant as possible during the whole of the fermentation. Any 
considerable rise in temperature accelerates the action of the yeast, but 
at the same time, and to a greater degree, stimulates lactic and other 



318 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

foreign fermentation. Good yeast works well at from 80° to 85° F., and 
at that temperature, lactic and butyric fermentation proceed but slowly, 
even in the presence of the special organisms which induce these types 
-of fermentation. Sudden cold should also be avoided, as a chill to 
working yeast is most detrimental, causing fermentation to entirely 
.cease, or at the best to proceed most sluggishly. Such a sudden lower- 
ing of temperature acts more severely on the yeast than on the disease 
ferments which may be present ; consequently during the time taken 
by the yeast to recover itself, its very inactivity becomes the foreign 
ferment's opportunity, and a chilled dough too often results in a sour 
loaf. 

399. Use Of Salt. — A great deal has been written as to the use of 
salt as a guiding agent in fermentation ; so far as the yeast is concerned, 
salt is generally viewed as having a retarding influence ; although the 
opinion has been expressed that quantities of salt under 3 per cent, of 
the water used stimulates the action of yeast. This opinion is based on 
certain observations of Liebig. The author's own experiments (vide 
chapter XI., paragraph 271) lead him to conclude that salt, in all pro- 
portions from 1-4 per cent, upwards, retards alcoholic fermentation, 
and diminishes the speed of gas evolution. Salt acts still more power- 
fully as a retarding agent on lactic and other foreign ferments, and so 
aids in the prevention of unhealthy fermentation. In addition, salt also 
checks diastasis, and thereby prevents undue hydrolysis of the starch of 
the flour. In summer time, or when any suspicion of instability 
attaches to the flour, it is well to add some portion of the salt to the 
sponge ; but when the flour is good, and the yeast pure and healthy, 
the whole of the salt may with advantage be deferred to the dough stage. 

In the Scotch methods of breadmaking, flours of ft very strong and 
stable character are used in the sponge, which altogether is allowed to 
stand about twelve hours. A slight amount of lactic acidity is 
developed in this, and is viewed as normal; it has an important 
function in softening and mellowing the gluten. It will be noticed 
that a small proportion of salt is, in the Scotch process, added to the 
sponge. 

400. LOSS during Fermentation. — This has been variously 
estimated, among the highest figures being that of Dauglish, who ex- 
pressed the opinion that this loss amounted to from 3 to 6 per cent. 
In order to determine the maximum amount of loss possible, the author 
made a direct experiment — 100 parts by weight of soft flour from 
English wheats were made into a dough with distilled water, two parts 
of pressed yeast being added; no salt being used. This dough was 

. allowed to stand for from eight to nine hours at a temperature of about 
85° to 90° F. ; fermentation proceeded violently, but towards the end of 
the time had apparently ceased. The dough was then placed in a hot- 
water oven, and maintained at a constant temperature of 212° F. for 
10 days; the same weight of flour and yeast, but no water, was also 
placed in the oven. At the end of the time the fermented dough was 
found to have lost 2*5 per cent, compared with the flour. Now in this 

. extreme case a soft flour was used with distilled water and no salt, and 



BREADMAKING. 319 



about six times the normal amount of yeast ; the temperature was pur- 
posely maintained at a high point, and the fermentation carried on so 
long as any decided evolution of gas occured. Yet, under these 
conditions, which far and away exceed in severity any such as are met 
with in practice, the loss was less than Dauglish's minimum estimate. 
It will be of interest to notice that the percentage of loss closely 
corresponds with that of sugar in flour, according to the analysis given 
in paragraph 270, chapter XL "Tablier Blanc," in the "British and 
Foreign Confectioner," states, as the result of experiments of his own, 
that the loss of solid constituents of flour during fermentation, as 
practically conducted in bakeries, amounts to 1*37 per cent. Turning 
next to the loss in weight of the dough during fermentation — Thorns 
gives, as the result of direct tests on the dough from a sack of flour, the 
loss during working as from 10 to 12 lbs., or from 3*5 to 4-2 percent. 
Dauglish's estimate was probably based on somewhat similar data; 
but a moment's consideration shows that this loss must consist largely 
of water which escapes by evaporation from the dough during 
fermentation. 

401. Baking. — For baking, the oven should be at a temperature of 
450-500° F. Many modern ovens are now fitted with a pyrometer, by 
means of which the temperature may be read off. If depending on this 
instrument, care must be taken that it is in efficient working order. In 
the oven the dough rapidly swells from the expansion of the gases 
within the loaf by the heat. Its outside is converted into a crust ; the 
starch being changed into gum and sugar : these are at the high tem- 
perature slightly caramelised, and so give the crust its characteristic 
colour. The effect of the heat on the interior of each loaf is to evaporate 
a portion of the water present in the dough : the carbon dioxide, and 
a portion of the alcohol produced by fermentation, escape with the 
steam, and may be recovered from the gases within the oven. While 
any water is present in the bread, the temperature of its interior can 
never rise above the boiling point of that liquid. Owing to the pressure 
caused by the confining action of the crust, that boiling point may, 
however, be somewhat higher than under normal atmospheric pressure. 
The increase due from this cause is probably not more than some two 
or three degrees. As baked bread still contains some 35 to 40 per 
cent, of moisture, it may be safely stated that the inside of the loaf 
never rises to a higher temperature than 215° F. At this temperature 
the starch cells will have burst ; the coagulable albuminoids will have 
been coagulated, and their diastasic power entirely destroyed. The 
composition of bread, compared with that of flour, is dealt with subse- 
quently. 

402. Time necessary for Baking. — The time during which 

bread is kept in the oven varies considerably in different parts of the 
country : much must depend on the temperature — whether the oven be 
quick or slack. For 4 lb. loaves an hour seems to be an average time. 
The half -quartern, or 2 lb. loaf, is a much commoner size in the south 
of England, and loaves of this description can readily be baked in forty 
minutes in any well constructed oven. 



320 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

403. Glazing. — On the admission of steam to an oven the dex- 
trinising of the starch of the crust goes on even more rapidly than 
ordinarily ; the effect is to produce a glazed surface on the outside of 
the crust : this operation is familiar to bakers as that by which French 
or Vienna rolls are glazed. The steam, on being admitted to the oven,, 
soon gains the same temperature as the interior of the oven itself, that 
is, 450-500° F. The bread is thus enveloped in an atmosphere of dry 
or superheated steam : this retards the rapid evaporation from the 
exterior of the crust, which is thus kept moister; with, as before 
explained, the more rapid conversion of the starch into dextrin. The 
steam is usually generated in a boiler placed as near as convenient to 
the oven : its pressure is immaterial, but may conveniently be about 25 
to 30 lbs. per square inch. 

The injection of steam into the oven, not only helps to dextrinise 
and glaze the crust, but also serves the purpose of keeping the interior 
of the loaf moist by preventing too rapid evaporation. 

As is well known, the ordinary baker's oven is heated to the baking 
temperature before the bread is introduced : the baking is then con- 
ducted at the expense of the heat of the brickwork of the oven. After 
baking one or more batches the oven will have become so cool as to 
require re-firing before it can properly bake any more bread. In an 
oven of this type the bread is therefore baked in what is practically an 
air-tight hot box : the evaporation from the dough speedily charges its 
atmosphere with steam, and this acts in the same manner, though to a 
less degree, as steam when injected into the oven. This proper confin- 
ing the steam within an oven is a point of great importance ; for with 
an " oven which loses her steam " the bread bakes slowly and is dry and 
chippy. In consequence, it is absolutely necessary that oven doors and 
other fittings should fit with extreme accuracy. Messrs. Graham & 
Sons, the well-known manufacturers of oven fittings, justly make it their 
boast that if a strip of tissue paper be shut any where between the door 
and its frame it is impossible to withdraw it whole. This end is secured 
by cutting a groove in the frame, into which fits a bead on the door; 
this and careful grinding both of the face of the door and its frame 
ensures a very perfect fit. 

404. "Solid" and "Flash" Beats.— These terms are fre- 
quently used by the baker in speaking of the character of the heat of 
different ovens. The former is applied to heat which is continuous, the 
latter to heat which is very temporary, but frequently for the moment, 
intense. It will be found that the so-called " solid " heat is usually 
evolved from the walls of a well-heated oven. A good oven should have 
plenty of material about it ; this gets hot through and afterwards radi- 
ates heat slowly but continuously. If the oven walls be too thin they 
cool too quickly ; in consequence they have to be heated very intensely 
at the start ; the result is that the oven at first burns the bread, and 
towards the end has not heat enough to complete the baking of the 
batch. With thicker walls the initial temperature of the oven need not 
be so high ; the fall in temperature taking place more slowly, the oven 
still retains a good heat at the close of the baking. The heat which 
reaches the bread from the walls of the oven is largely in the form 



BREADMAKING. 321 



known as " radiant " heat ; it is continuous, and need not be of abnor- 
mally high temperature in order to thoroughly and efficiently bake 
bread. The consequence is that the interior of the bread is well baked, 
while the crust is not burned. 

A "flash" heat, on the other hand, is produced by the contact of 
highly heated gases with the bread. Certain varieties of ovens are 
fired by the introduction of flame into the oven itself. Such intro- 
duction of flame should be employed to previously raise the temperature 
of the oven, not, except possibly as an auxiliary, to bake the bread 
itself. The reason is obvious ; it is exceedingly difficult to regulate the 
temperature of a current of hot air from a flame with great exactitude. 
The temperature is sufficiently high at one time to burn the crust ; at 
another so low as to prevent, during the time the bread is in the oven, 
its inside being sufficiently cooked. Further, if the bread is to be 
heated by the hot air resulting from the direct admission of flame into 
the oven, there must necessarily be also some means of exit for the gases 
from the flame. The hot air from a furnace cannot, in fact, be drawn 
into the oven without some means for their after escape. The result is 
that these gases carry with them the steam evolved from the baking 
loaves, and so subject the bread to a dry, instead of a steam saturated, 
atmosphere. The author's advice is, however the oven be heated, let 
it during the actual time of baking be kept as air-tight as possible, 
letting the bread be baked by radiant heat, and not the mere contact of 
heated gases. 

405. Cooling Of Bread. — The loaves on being taken from the 
oven should be cooled as rapidly as possible in a pure atmosphere ; for 
this purpose, where practicable, open-air cooling sheds should be pro- 
vided. Failing these, the cooling-room must be well ventilated. It 
goes without saying that the cooling loaves must be adequately pro- 
tected from rain. 

406. Souring Of Bread. — Differences of opinion exist as to 
whether the act of baking destroys the life of all organisms that may be 
present in the dough. Unless the baking is most inefficiently con- 
ducted, the temperature within the loaf should be sufficiently high to 
kill the yeast. The doubt is whether or not the germs or spores of 
other organisms are also destroyed — thus the spores of some of the 
bacilli can withstand a quarter of an hour's boiling, while a sensible 
proportion outlive an hour's subjection to a boiling heat. These ex- 
periments afford grounds for supposing that such germs might continue 
to exist even during an hour's baking. The observed facts of the sour- 
ing of bread also point in the same direction. Two loaves may be taken, 
each of which is sweet when removed from the oven, and kept under 
precisely the same conditions ; the one after a few hours becomes sour, 
the other retains its sweetness. Here there is a difference in behaviour 
which is not due to external conditions, but to some inherent quality of 
the two loaves. An investigation of the previous history of the bread 
will show that the one has been fermented with a sound, the other with 
an unhealthy yeast. The undestroyed germs of acid fermentation have, 
in the bread in which they are present, induced sourness. The only 



322 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

other explanation of souring is that the germs of the specific bacilli have 
found their way from the atmosphere into the baked loaf. In illustra- 
tion there may be cited a most striking instance of this souring of a 
loaf of bread, which a short time ago came under the notice of the 
author. While in a friend's room on one of the upper floors of some 
London offices, a batch of four loaves of bread, just hot from the oven, 
was brought in. The loaves were in every way triumphs of the baker's 
art — they smelt perfectly sweet, and evinced not the slightest vestige of 
any sour odour. One loaf was broken from the batch and taken, while 
still warm, to a crowded room, containing perhaps from 300 to 400 
people ; the room was also not ventilated in the most efficient manner. 
After remaining in this room about two and a half hours the loaf was 
broken, and emitted a decidedly sour odour. The three loaves which 
had been kept in the cool office in pure air were found next morning to 
be perfectly fresh and sweet. The only difference between these loaves 
was that one had cooled slowly in the warm atmosphere, the other 
rapidly in a pure atmosphere. Even in the space of two hours an acid 
fermentation had been set up. 

The foregoing paragraphs will have shown what are at least some of 
the causes for bread becoming sour ; a summing up of these, together 
with suggestions as to remedies, will appropriately follow the next 
paragraph. 

407. Sanitary Aspects of Bakehouses.— This is a most 

important problem, not only to the baker, but also to the general public. 
The following paragraphs contain suggestions as to what should be aimed 
at, and what avoided, in bakehouse-building management. Many will 
probably feel that the adoption of such suggestions as are given would 
be to them impracticable. That they are not Utopian is shown by their 
being in every case based on practical experience of the nature and 
arrangements of the best managed bakehouses in the kingdom. It 
must be remembered that the general public is now demanding, none 
too soon, that the whole operation of breadmaking shall be conducted 
with the most scrupulous cleanliness. The bakers who will in the 
future command success are those who move in advance of this per- 
fectly reasonable demand. 

The right and proper position for a bakehouse is on the ground floor : 
it is to be deplored that much of our bread is baked in cellars. Circum- 
stances may render it impossible for individual bakers to manage 
otherwise than to have the bakery perhaps underneath the shop ; but 
wherever this arrangement has to be adopted it must be viewed as an 
unfortunate necessity, not as a thing to be commended or justified. In 
large towns the plea is that space is so valuable that it is impossible to 
devote the ground floor to the purposes of a bakehouse. In such cases, 
undoubtedly, the correct principle of supplying bread is that the bake- 
house should be in the suburbs, and depots, for sale only, in the more 
crowded thoroughfares. Evidence is not wanting that, as an unavoid- 
able effect of economic laws, the business of breadmaking is already 
tending in this direction. The smaller baker can best justify the 
continuance of the present system by absolute cleanliness and healthiness 
of the arrangements and management of his premises. Let him 



BREADMAKING. 323 



remember that a vigilant and competent man can superintend a small 
business, giving personal supervision to every detail ; a thing which is 
much more difficult, if not impossible, with operations conducted on a 
larger scale. 

The bakehouse should be well lighted, for there is no greater enemy 
to dirt than light. As sudden draughts are so prejudicial to fermenta- 
tion, there should be sufficient space to permit of efficient ventilation 
without strong currents of cold air. The bakehouse itself may be 
covered with glazed tiles, which should be carefully washed from time 
to time ; or, in place of tiles, the recommendation of a practical baker 
may be followed, and the bakery lime-washed. Notice that lime-wash 
is to be used ; not a mixture of size and whiting. Size, being a nitro- 
genous body of animal origin, is peculiarly liable to decay, and may thus 
become the harbour of ferments, which are pretty sure to contain 
among their number some whose action will be injurious. Whiting is 
a, carbonate of lime, and is practically without action on ferments. 
Lime- wash that has been made from recently slacked quicklime, contains 
lime in the caustic state, and so is fatal to any ferments with which it 
comes in contact. A bakery should frequently be thoroughly cleaned 
down and white- washed. The lime brush must find its way into every 
nook and cranny. 

A sufficient supply of hot and cold water must be provided; the 
former usually being obtained from a boiler heated by the waste gases 
from the oven. 

No drains directly connected with the sewer must be permitted in 
the bakehouse. Wherever there is a sink fixed, the waste pipe must be 
carried from it through the wall, and allowed to discharge over an 
efficiently trapped drain, with which it is not in contact. The floor 
should be either well bricked or made of concrete, in such a manner 
as to prevent any spilled water lying in pools or soaking into the earth 
beneath. If the ovens are fired from within the bakehouse, sufficient 
provision must be made to prevent either coal-dust or ashes finding 
their way over it. Any pouring of waste water, either on the coal or 
into the ash-pit, should be sternly prohibited. 

If, perforce, the bakehouse is in the basement, then special provision 
must be made for sufficient ventilation : the nature of such provision 
must depend on circumstances. If possible, the bakehouse should open 
on to a fair-sized area at either back or front ; this enables a current 
of fresh air to be admitted, while openings guarded by gratings should 
be made near the top of the walls to facilitate the escape of the vitiated 
air. The remarks about drains apply with even more force to under- 
ground bakeries : situated as they are, they are even more liable to 
incursions of foul gas from sewers, if any drains open direct into them. 
The rule without exception should be, carry all waste pipes out of doors, 
and let them discharge over a well-trapped drain. 

Whether the bakehouse be above or underground, no accumulation 
of ashes, scraps of dough, or rubbish of any description, must be tolerated 
for a moment. 

Workmen's offices and conveniences should be provided absolutely 
apart from the bakehouse. Closets must on no account open into the 



324 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

bakehouse : the objection does not apply so powerfully to washing ap- 
pliances, but even those are far better in a separate room. Except in 
those situations so absolutely unfitted for a bakehouse, that every square 
inch of space has to be utilised for the bakehouse itself, the provision 
of such accommodation can easily and cheaply be made. 

Ferment tubs and similar vessels should be washed with hot water 
every time after use ; they are all the better for being occasionally 
steamed out with a jet of naked steam from the boiler. This may be 
led down by a piece of flexible hose to the bottom of the tub, which 
must be covered over so as to keep the steam in during the operation. 
Troughs and boards should be scraped clean each day ; no vestiges of 
dough must be permitted to remain either in the corners of the troughs 
or cracks of the boards. Once a week they should be washed and 
scrubbed and then wiped as dry as possible : they must then be left 
open in the warm bakehouse so as to drive off the last vestiges of mois- 
ture. Damp troughs and boards have a great tendency to become sour. 

408 Remedies for Sour Bread. — As one possible cause for 

sour bread is a want of absolute cleanliness, it should be seen that the 
above precautions, or their equivalent, are rigidly adopted. Supposing, 
as is sometimes the case, that batch after batch of bread is sour, or 
rapidly becomes so ; then see that the flour is sound ; next examine the 
yeast ; see more especially whether disease ferments are plentiful, and 
whether the yeast-cells themselves look healthy and vigorous. The 
baker who is not able to do this for himself should place himself in the 
hands of an analyst to do it for him. If any suspicion whatever attaches 
to the yeast, change to some other variety which is known to be doing 
good work. In the next place, thoroughly clean the bakehouse from 
floor to ceiling. Procure some solution of bisulphite of lime, and with 
a brush wash floor, walls, and ceiling with it. Clean out all troughs and 
boards, and also wash them with the bisulphite, letting it remain in the 
troughs for some time. Then either scald or steam them out, and dry 
as rapidly as possible. These steps should succeed in freeing the bake- 
house from any disease ferments which may be present. 

In conducting fermentation, use a sufficient quantity of good yeast 
to get sponging and doughing over quickly, and work at a low tempera- 
ture. Give the bread a good baking, as bread which leaves the oven in 
a damp sodden condition is specially liable to become sour. When 
baked, cool rapidly in a pure atmosphere. Weak unstable flours used 
with excess of water very frequently turn sour ; the reason is that the 
gluten breaks down, and much of the starchy interior of the loaf is 
dextrinised : the damp clammy mass resulting, constitutes a favourable 
nidus, or home, for after fermentation. Summing up, sour bread is 
caused by the presence of the germs of the specific ferments which pro- 
duce acidity ; without these, bread cannot turn sour ; secondly, these 
germs of foreign ferments may be introduced along with the yeast, or 
may be present in fragments of old dough in the troughs and other 
utensils, or may be floating about in the atmosphere of the bakehouse 
through want of cleanliness and inefficient ventilation. The produc- 
tion of acidity is favoured by the use of weak, unhealthy yeast, 
unstable flours used with excess of water, fermentation being 



BREADMAKING. 325 



conducted at too high a temperature, insufficient baking, and 
cooling in a warm, impure atmosphere. 

409. Working with Unsound or very Low Grade Flours. 

— In the older literature of breadmaking it is interesting to read the 
directions given under this head ; when, through a bad harvest, wheat 
has either not ripened properly, or has after the reaping been badly 
wetted, great care is necessary in order to make a passable loaf of bread 
from the flour produced. Thanks to the abolition of the Corn Laws, 
the United Kingdom can now command the markets of the world, and 
without any difficulty secure sound wholesome wheats at a fair price. In 
the present day there is practically no excuse for a baker having a sack 
of unsound flour in his flour room. 

In composition the unsound flours have a low percentage of gluten, 
and that badly matured ; while the soluble albuminoids are high and in 
a comparatively active diastasic condition. The starch granules have 
their walls softened down and often fissured. The moisture is high, so 
also, owing to the degradation of starch and albuminoids, is the soluble 
extract. These flours are found on testing to be weak and unstable. 
So far as their treatment is concerned, that commences with the wheats 
rather than with the flours. A wheat harvested damp is not necessarily 
unsound ; these chemical changes are to a great extent an after con- 
sequence of the dampness. Such wheats should immediately on being 
harvested be kiln-dried at a gentle heat of about 38° C. (100° F.), until 
the moisture present is reduced to 10 per cent, of the whole grain. 
While the flour produced from the wheat thus treated may be weak, 
it will be fairly stable and not unsound. The gluten will be higher, 
and the soluble extract and albuminoids comparatively low. The ex- 
periments described in paragraph 368 of the preceding chapter show 
that even weak damp flours may be considerably improved by gentle 
kiln-drying of the flour itself. Such treatment is also by far the best 
that can be adopted with unsound flours ; those flours which are not 
amenable to it should be entirely rejected for breadmaking purposes. 

Having by preliminary treatment made the best of an unsound flour T 
it should be used in the dough, which should be got into the oven as 
speedily as possible. A little compressed yeast added at the dough 
stage will often be found of service by hastening the fermentation. As 
unsound flours are particularly liable to produce sour bread, special 
attention should be paid to the suggestions made in the preceding 
paragraph. Further reference to unsound flours will be found in the 
paragraphs describing other methods of aerating bread. 

The low grade flours of gradual reduction processes are, if from a 
sound wheat, perfectly sound in themselves ; yet they require some care 
in manipulation, because they contain the active diastasic constituent of 
the bran, cerealin, in considerable quantity. Where these flours are 
employed, a sponge should be prepared from a strong flour and the low 
grade used in the dough. 

410. Use of Alum, Copper Sulphate, and Lime— Alum, 

the double sulphate of aluminium and potassium, A1 2 K 2 (S0 4 ) 4 ,24H 2 0, 
was formerly largely used as an adulterant of bread. This, and the 



326 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

other substances mentioned, behave as retarding agents to diastasis - 7 
with unsound flours they prevent or lessen the degradation of the 
gluten and starch during fermentation, and so cause a loaf made from 
a bad flour to be larger, less sodden, and whiter, giving it the appear- 
ance of bread made from far better flour. So far, and considered from 
this aspect alone, the action of alum is remedial ; it prevents undesir- 
able changes occurring in the flour during fermentation. There is no 
doubt that by the use of alum, flour, so bad as to render breadmaking 
in the ordinary manner impossible with it, can be converted into eatable 
loaves ; but if necessity arises for recourse to such flours for bread- 
making, other processes are now known which achieve the same object 
by methods that are absolutely unobjectionable. The continued use of 
alum, even in small quantity, is, according to medical evidence, injurious 
to health : in particular, the alum remaining, as it does, unchanged in 
the bread, retards the digestive action of the secretions of the mouth 
and stomach. As alum is injurious, and as it is used with the 
object of enabling inferior flour to be substituted for that of 
good quality, to the prejudice of the consumer, it is rightly 
considered as an adulterant, and its use made penal. 

Minute quantities of copper sulphate, CuS0 4 , have also been em- 
ployed : its action is very similar to that of alum ; but as all copper 
salts are very poisonous, its use is even more reprehensible 
than that of the former adulterant. 

Liebig suggested the employment of lime in solution, lime-water, 
CaH 2 2 , as a means of preventing excessive diastasis during panary 
fermentation. This substance is quite as effective as alum so far as the 
effect on diastasis is concerned, but unlike alum it exerts very little 
retardation on the alcoholic fermentation caused by the yeast. Lime is 
soluble in about 780 parts of cold water : its solution, or what is com- 
monly called lime-water, may be prepared by adding about two ounces 
of recently burned quicklime to ten gallons of water, and stirring up. 
A better plan is to add the lime in considerable excess, stir thoroughly, 
and then allow the superfluous lime to settle. In a few hours the upper 
liquid becomes clear, and may be dipped off without disturbing the sedi- 
ment. Some more water may then be added and the mixture again 
stirred ; another quantity of lime-water is thus made. This operation 
may be repeated several times if sufficient lime has been taken in the 
first place. Any vessels containing lime-water have to be kept covered, 
as carbon dioxide is rapidly absorbed from the air, with the formation of 
calcium carbonate. Richardson states that Liebig's directions were 
that the flour and lime-water should be used in the ratio of 19 of flour 
to 5 of lime-water, and then goes on to say that that quantity of liquid 
not being sufficient to convert the flour into dough, the requisite quantity 
of ordinary water was added. He then proceeds to quote an experiment 
in which 1 9 lbs. of flour were made into bread with ordinary water, and 
yielded 24 lbs. 8 oz. of bread. A like quantity of the same flour, 
kneaded with 5 quarts of lime-water, produced 26 lbs. 6 oz. of bread. 
There is evidently a mistake here somewhere, 5 quarts of water to 19 lbs. 
of flour means 73 quarts of water to the sack; this quantity so far from 
not being sufficient to convert the flour into dough is something like 



BREADMAKING. 327 



10 quarts more water than is ordinarily used by the London baker. 
As, on the continent, the metric system of weights and measures is that 
commonly used ; Liebig's ratio was in all probability 1 9 kilograms of 
flour to 5 litres of water, the exact English equivalent of which would 
be 19 lbs. of flour to 5 lbs., or two quarts of water : this equals 29 
quarts of lime-water to the sack. The deficiency is then made up by 
the addition of ordinary water. The baker, desiring to use lime-water, 
may make it and employ it in the proportion just stated, or he may add 
not more than 1 J ounces of lime to the water per sack of flour. In this 
latter case he must stir the water thoroughly so as to ensure the com- 
plete solution of the lime : a milkiness throughout the whole of the 
water would not hurt, but any lumps must be avoided. The safest 
method is to prepare the lime-water as a previous operation. Lime- 
water is used by some of the Glasgow bakers, who advertise bread con- 
taining, it as a speciality. The bread made with lime-water is more 
spongy in texture, pleasant to taste, and quite free from sourness. In 
the finished bread, the lime no longer exists as free alkali, because the 
carbon dioxide gas generated during fermentation will have completely 
changed it into calcium carbonate — 



CaH 2 2 


+ co 2 = 


CaC0 3 


+ 


H 2 


Lime. 


Carbon Dioxide. 


Calcium 
Carbonate. 




Water. 



Calcium carbonate, which is identical in composition with chalk, has in 
small quantities no deleterious action when taken into the system. 

So far as Richardson's quotation of experiment may be depended on, 
it indicates an increased yield of bread by the use of lime-water : he 
ascribes this increase to the loss caused by fermentation when working 
in the ordinary manner; but his views on this subject have already been 
shown to be fallacious. The true explanation is a very simple one ; the 
lime-water, by preventing the degradation of the gluten and the diastasis 
of the starch, increases the water-retaining power of the flour, and so 
enables the same weight to yield a greater quantity of bread. 

411. Special Methods of Breadmaking. — There are certain 

special processes employed for bread-making which must next be de- 
scribed. 

412. "Vienna Bread." — This is the name applied to rolls and 
other light fancy bread. Vienna bread is made with patent flour and 
compressed yeast. No potatoes or ferment is used. Instead of water, 
the bread is sometimes made with milk or a mixture of milk and water. 
The following recipe is quoted from " The Miller" : — 

Proportions. — 8 lbs. of flour, 3 quarts of milk and water in equal pro- 
portions, 3 \ ounces of compressed yeast, and 1 ounce of salt. The warm 
water is first mixed with the milk, so as to give a temperature of from 
80 to 85° F. Sufficient flour is then added to make a weak sponge, not 
much thicker than a batter. The yeast is crumbled, mixed well in, 
and the sponge allowed to stand for about forty-five minutes. The rest 
of the flour is next added slowly, together with the salt ; the dough is 
then thoroughly kneaded and set to ferment for 2 J hours. All 
Hungarian flour may be used throughout, or the finest Spring American 



328 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Patent may be substituted in the sponge. The bread is glazed during 
baking by the introduction of a jet of steam into the oven. 

413. Leavened Bread. — In France and other parts of the 
Continent bread is made from leaven, which consists of a portion of 
dough held over from the previous baking. The following description 
is given on the authority of Watt's Dictionary of Chemistry. A lump 
of dough from the preceding batch of bread is preserved ; this weighs 
about twelve pounds, made up of eight pounds of flour to four of water, 
and is the fresh leaven (levain de chef). This fresh leaven, after re- 
maining for about ten hours, is kneaded in with an equal quantity of 
fresh flour and water, and thus produces the levain de premiere ; again, 
this is allowed to stand for some hours (about eight), and is kneaded in 
with more flour and water. After another interval of three hours, 
100 lbs. of flour, 52 of water, and about \ lb. of beer yeast are added; 
this produces the finished leaven (levain de tout 'point). The finished 
leaven weighs about 200 lbs., and is mixed, after standing two hours, 
with 132 lbs. of flour, 68 lbs. of water, \ lb. yeast, and 2 lbs. of salt. 
The dough thus formed is divided into two moieties, the one is cut into 
loaves, which are kept for a time at a moderate temperature (77° F.) 
and then baked. The bread thus produced is sour in taste and dark in 
colour. The remaining half of the dough is kneaded with more flour, 
water, yeast, and salt, and divided into halves ; the one quantity is 
made into loaves, which are allowed to ferment -and then baked; the 
other is subjected again to operation of mixing with more flour, &c, 
and working as before. This sub-division is repeated three times ; the 
bread improving at each stage, and the finest and whitest loaves being- 
produced in the last batch. Readers will, doubtless, have already 
noticed that as the quantity of leaven decreases, and that of yeast in- 
creases, the quality of the bread improves. In the latter stages, they 
" reform the leaven indifferently ; " the English baker is in this matter 
more logical, and " reforms it altogether." As a consequence, he pro- 
duces from flour and yeast a bread better as a whole than that re- 
sulting from the complicated French system of leavening. This mode 
of breadmaking seems now to have largely given place to methods more 
nearly allied to Viennese and English processes. 

414. Other Theories of Panary Fermentation— Mege- 

MourieS. — Among descriptions of the phenomena of panification, that 
by Mege-Mouries, written in 1860, and translated for " The Miller" in 
1881, is of interest, as an account of the views held before the develop- 
ment of the Science of Fermentation as at present understood. During 
the process of leavening, Mege-Mouries recognised that alcoholic and acid 
fermentation proceeded simultaneously. Quoting his own words, " the 
acid fermentation produces the acid requisite for dissolving a portion of 
the gluten, and rendering it suitable for forming an alcoholic ferment 
under the action of the alcoholic ferment already formed." He further 
goes on to state that the gluten develops the alcoholic ferment, and the 
casein, the lactic ferment ; also that cerealin, if introduced, rapidly pro- 
duces a large quantity of lactic acid. This " acid dissolves the gluten, 
which thus becomes a lactic ferment." A more exact knowledge of the 



BREADMAKING. 329 



phenomena of fermentation, for which we are indebted to Mege-Mouries' 
illustrious countryman, Pasteur, shows the untenability of these 
opinions ; as it is now known that fermentation is the work of distinct 
organisms, and not a peculiar property of albuminous compounds in 
certain phases of decomposition. Mege-Mouries asserts that the 
diastasic action of the embryous, or cerealin membrane, resists a tem- 
perature of 212° F. ; in making this statement he is, however, at 
variance with other observers, whose experiments have been made with 
every precaution for exactitude. The reader is referred to chapters VII. 
and VIII. for a detailed account of diastasic action generally. Mege- 
Mouries' researches marked a distinct step of advance in the scientific 
knowledge of flour and breadmaking ; but a quarter of a century has 
elapsed since they were first published, and during that time more 
recent discoveries have so modified scientific views of fermentation that 
Mege Mouries' explanations could not now be accepted. His statements 
of fact are nevertheless of great value, and it is specially interesting to 
notice his insistance on the diastasis produced during panification by 
the cerealin of the inner membrane of the bran. The thorough removal 
•of this integument by modern milling processes, coupled with the 
universal employment of yeast in this country instead of leaven, causes 
his remarks on this subject to no longer have the practical bearing they 
possessed when first written. The student of the history of the science 
of wheat and wheat-bread will find Mege-Mouries' papers well worth 
reading. 

415. Recent Researches by Chicandard.— In May, 1883, 

Chicandard communicated to the Academy of Sciences, Paris, a theory 
of panification adopted by him as the result of recent researches. He 
first expressly states that his conclusions do not apply to fermentation 
:as conducted in England, but to bread made on the leaven system. 
English bread is excepted because of its being customary to add potatoes 
to the ferment, the gelatinised starch of which he admits may be sus- 
ceptible of alcoholic fermentation. But as many English bakers make 
their bread from flour, yeast, salt, and water only, any alcoholic fer- 
mentation which occurs cannot be explained by the general statement 
that English bakers use fruit. Briefly summing up Chicandard's 
conclusions, they are — " The fermentation of bread does not consist in 
the hydrolysis of starch, followed by alcoholic fermentation, and is not 
determined by Saccharomyces, but is a result of the solution and after 
peptonisation of the gluten, this effect being caused by a bacterium, 
~which develops itself normally in the dough, yeast merely accelerating 
its development." 

The author has shown that the saccharine matters of flour are in 
themselves sufficient to account for all gas evolved during fermentation, 
and that active fermentation ceases with the total disappearance of the 
sugar : there is no need therefore for the hydrolysis of the starch, as a 
preliminary to alcoholic fermentation. In proof that the gas evolved 
during panification is not the result of alcoholic fermentation, Chicandard 
states that the presence of alcohol has never been proved : in this he is 
contradicted by Moussette, who detected alcohol in the gases of an oven 
in use in France, so early as 1854, and at a time when the bread was 



330 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

undoubtedly being made by the leaven process. Chicandard looks upon 
bread fermentation as being due to bacterial fermentation of the gluten 
present : such fermentation is a concomitant of putrefaction, and does 
cause the slow evolution of gas. To a certain extent in leavened dough 
the gas may be thus produced, but no such explanation is possible of 
the fermentation of a mixture of flour and water only, with pure yeast. 
Previously quoted experiments have demonstrated that the functioning 
of living'yeast is positively inimical to bacterial development, although 
the albuminous contents of ruptured yeast cells afford a suitable nidus 
for bacterial growth. In a further communication, Chicandard states 
that he made a dough with flour, dextrose, yeast and water, testing it 
immediately on being made, and again after standing three and seven 
days respectively : he found in each case that 10 grams of the dough- 
contained 0*55 grams of dextrose. These results are absolutely contra- 
dicted by the author's experiments on fermentation of aqueous extract 
of flour ; these show conclusively that all the sugar disappears, and, 
what is of equal importance, that the yeast does not evolve gas from the 
albuminoids. That Chicandard found precisely the same amount of 
dextrose at the end of seven days as he found at the commencement is 
remarkable, considering that during the whole of that time more or less 
starch is being converted by diastasis into dextrin and saccharine com- 
pounds. Chicandard points out that during panification the yeast cells 
gradually disappear ; the best explanation known to the author, of this 
phenomenon is that advanced by Thorns, who avers that, as yeast cells 
function in dough, they disappear through the breaking down of the 
cell-walls. This view has been adopted in the present work. With the 
same observer's opinion that yeast, in dough, functions on the albumin- 
ous rather than the saccharine matters, the author cannot agree, for the 
reasons given in the conclusions he has drawn from his own experiments. 
Girard has since pointed out in the " Comptes Rendus," that he has 
examined the gas contained in dough at various stages of preparation, 
and finds it to consist mainly of carbon dioxide, mixed with the air 
originally contained in the flour. In some cases, part of the oxygen 
had been absorbed, most probably, Girard thinks, as a consequence of 
the secondary formation of acetic acid. [The author's opinion is that 
this absorption is due to the direct action of the yeast ; which organism, 
as has been already demonstrated, exhibits a remarkable avidity for 
oxygen.] On mixing the dough with water and distilling, the distillate 
was found to contain alcohol in quantity amounting to 3*15 c.c. or 2*5 
grams, per kilogram of dough. The same results were obtained whether 
the dough was mixed with leaven or with yeast ; thus affording addi- 
tional evidence that the rising of dough is due to alcoholic fermentation. 

416. Methods of iErating Bread other than by Yeast. — 

Carbon dioxide is not only produced by alcoholic fermentation, but may 
also be generated within dough by purely chemical means, or may be- 
mechanically introduced by first effecting its solution in water. 

417. Baking Powders. — The carbon dioxide gas within the 
dough is sometimes generated by the action of baking powders of various, 
kinds ; these are mixtures which, under the influence of either water or 



BREADMAKING. 331 



heat, evolve carbon dioxide. Those which effervesce on the addition of 
water consist of an acid and a carbonate, usually the bicarbonate or 
acid carbonate of soda ; the acid employed is generally tartaric acid. 
On the addition of water a change occurs, which is illustrated in the 
following equation : — 

H 2 C 4 H 4 6 + 2NaHC0 3 = Na 2 C 4 H 4 6 + 2H 2 + 2C0 2 

Tartaric Acid. Sodium Bicarbonate. Sodium Tartrate. Water. Carbon Dioxide 

Instead of tartaric acid, cream of tartar, KHC 4 H 4 6 , is sometimes 
employed ; the reaction then becomes : — 

KHC 4 H 4 6 + NaHC0 3 = KNaC 4 H 4 6 + H 2 + C0 2 

Cream of Tartar. Sodium Bicarbonate. Potassium Sodium Water. Carbon Dioxide. 

Tartrate. 

Potassium sodium tartrate is sometimes termed " Rochelle Salts." 
The sodium bicarbonate is also decomposed by the action of heat ; on 
heating its solution, carbon dioxide gas is evolved, with the formation 
at first of a so-called sesquicarbonate, and afterward of the normal 
carbonate. This latter body is thus formed : — 

2NaHCO s = Na 2 C0 3 + H 2 + C0 2 

Sodium Bicarbonate. Sodium Carbonate. Water. Carbon Dioxide. 

One of the carbonates of ammonium is also sometimes used as a source 
of carbon dioxide gas ; a solution of the bicarbonate, on being heated, 
is decomposed according to the following equation : — 

2(NH 4 )HC0 3 = (NH 4 ) 2 C0 3 + H 2 + C0 2 

Ammonium Bicarbonate. Ammonium Carbonate. Water. Carbon Dioxide. 

The commercial ammonium carbonate is a sesquicarbonate; it, 
however, continuously evolves ammonia, being slowly changed into the 
bicarbonate. 

In the manufacture of baking powders, the tartaric acid or cream of 
tartar, together with the proportionate quantity of bicarbonate of soda, 
is mixed with air dried starch. This latter component increases the 
weight of the baking powder ; it also, owing to the hygroscopic nature 
of starch, helps to keep the active ingredients free from moisture. 
Unfortunately commercial tartaric acid and cream of tartar frequently 
contain lead, and this metal is a very dangerous poison, as even when 
taken in small quantities its effects accumulate in the system. The 
resultant tartrates all possess an aperient action — hence their continued 
use is to be deprecated. 

From time to time various substitutes for tartaric acid in baking 
powders have been proposed : among these is the bisulphate of potash, 
KHS0 4 ; a baking powder, containing this as its active acid ingredient, 
was some short time ago patented and extensively advertised under a 
special name, very similar to " tartaric acid." Sulphate of potash, which 
is produced when this substance is neutralised by sodium bicarbonate, is 
a powerful purgative, and so is absolutely unfitted for introduction into 
bread. Alum is at times also used as an adulterant of baking powder. 

As substitutes for tartaric acid or cream of tartar in baking powders, 
phosphoric acid, and the acid or biphosphates of lime, potash and 
ammonia are now employed : these substances are cheaper than the 
tartaric compounds, and can readily be obtained free from lead and 
other metallic impurities. They readily evolve carbon dioxide when 



332 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

their mixture with the sodium bicarbonate is dissolved in water. The 
resultant phosphates have but a very slight and harmless aperient 
action. 

418. Self- Raising Flour.— The articles sold under this name 
consist of flour, mixed with acid phosphates, and the bicarbonate of 
soda : as with baking powder, the addition of water causes the evolution 
of gas. Self-raising flours may be viewed as being flours sold with 
baking powder already mixed with them. It is claimed for the use of 
phosphates in this manner that it replaces these important salts, which 
are removed from the wheat in the bran. 

419. Use Of Hydrochloric Acid.— In the manufacture of whole 
meal bread it is customary to employ hydrochloric acid and sodium 
carbonate in the exact proportions in which they neutralise each other : 
they then not only evolve carbon dioxide gas, but also yield sodium 
chloride, or common salt, thus : — 

NaHC0 3 + HC1 - NaCl + H 2 + C0 2 

Sodium Hydrochloric Sodium Water. Carbon 

Bicarbonate. acid. chloride. dioxide. 

The salt thus formed lessens the quantity which otherwise would 
have to be added to the bread. Great care is requisite in the proper 
mixing of the acid and the carbonate with the meal : it is also import- 
ant that exactly the right proportions should be taken. A rough 
measurement of the strength of the acid may be made by taking a 
weighed quantity, say an ounce, of the bicarbonate of soda, dissolving it 
in boiling water in a beaker, and then adding a few drops of litmus 
solution. The hydrochloric acid should be measured, or else a quantity 
placed in a beaker, and weighed in it : then add the acid little by 
little until one drop changes the colour of the bicarbonate of soda solu- 
tion from blue to red. Then, again weigh the acid containing beaker ; 
the loss in weight gives the quantity of the hydrochloric acid, equiva- 
lent to an ounce of the bicarbonate. Commercial hydrochloric acid is 
usually sold with a guaranteed density of 1*15 ; this is equivalent to 
about 30 per cent, of the anhydrous acid. As 84 parts of sodium 
bicarbonate are exactly neutralised by 36*5 of anhydrous hydrochloric 
acid, and as this amount is contained in 122 parts of the commercial 
acid, the bicarbonate of soda and hydrochloric acid of this density should 
be used in the proportions of 84 of the bicarbonate to 122 of the acid, 
or practically in the proportions of 2 to 3 by weight. It has been 
recommended that 3 lbs. each of the acid and bicarbonate be used to 
the sack of flour : these proportions leave, however, a considerable 
excess of the carbonate in the bread. The great objection to the 
hydrochloric acid method is that the commercial acid almost invariably 
contains traces of arsenic, and thus a minute quantity finds its way 
into the loaf. 

420. Whole Meal Bread. — It is principally in making whole 
meal bread that the hydrochloric acid and bicarbonate method is em- 
ployed. The reason is that, with the presence of the bran, cerealin is 
introduced into the dough in such quantity that if ordinary fermenta- 
tion processes be employed diastasis proceeds to a very serious extent. 
The excess of dextrin thus produced causes the dough to become soft 



BREADMAKING. 333 



and clammy, and so to offer a matrix in which sour and other unhealthy 
fermentations are apt to proceed rapidly. The brown colour is due to 
the excess of dextrinous matter contained in the bread. The rapidity 
of the acid treatment enables the bread to be got into the oven before 
diastasic action can have proceeded to any extent. When the ferment- 
ation method is employed for making whole-meal bread, it is customary 
to make a sponge with a small quantity of very strong flour, and only 
add the whole meal at the dough stage. However made, whole meal 
bread has a great tendency to become sodden : in order to drive off 
excess of moisture it has to be baked for a considerable time, conse- 
quently the loaf has often a very thick crust while the interior is still 
unduly moist. In summer time particularly, the making of whole meal 
bread is an unsatisfactory operation, as great difficulty is often experi- 
enced in producing a sound and well-risen loaf. The whole of the pre- 
cautions necessary in the manufacture of whole-meal bread are strongly 
suggestive of the unsuitability of such meal for the purposes of making- 
bread at all. It is to be deplored that, for the sake of getting the 
nutriment supposed to be contained in the bran, a section of the public 
should demand a form of bread so unhealthy in other respects. 

In all the operations just described, carbon dioxide is formed in 
dough, and thus raises it. The chemical action which under these cir- 
cumstances takes place is not, however, a complete representative of 
that which occurs with yeast. One of the functions of this body during 
the fermentation of bread, is to act on the albuminoids, and also to a 
certain extent on the starch ; the result of such action, when normal, 
is to impart to the bread a characteristic flavour that can be obtained 
by no other means at present known. 

421. The iEration Process. — One other method of aerating 
bread remains for consideration, and that is the system associated with 
the name of Dr. Dauglish. The carbon dioxide is in this method pre- 
pared apart from the bread and forced into water under pressure ; this 
water, which is akin to the aerated water sold as a beverage, is then 
used for converting the flour into dough, the whole operation of knead- 
ing being performed in a specially prepared vessel in which the pressure 
is maintained. The kneading being completed, the dough is allowed to 
emerge from the kneading vessel, and immediately rises, from the ex- 
pansion within it of the dissolved carbon dioxide. Such was the nature 
of the method originally employed by Dauglish • but now the following 
modification is used : — A weak wort is made by mashing malt and flour; 
this is allowed to ferment until through the agency of bacteria it has 
become sour ; in all likelihood through the presence of lactic acid. The 
water to be aerated is first mixed with a portion of this weak acid 
liquid : it is then found to absorb the carbon dioxide gas much more 
readily. The acid also softens the gluten. So far as the actual aeration 
process is concerned, this method is mechanical rather than chemical. 
The great objection is that those more subtle changes, by which flavour 
is produced, do not occur here more than in the other purely chemical 
methods of breadmaking before described. A common experience in 
eating aerated bread for some time is that it, after a while, gives the 
impression of rawness. This is doubtless due to their being no such pep- 



334 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

tonisation of the albuminoids as results from fermentation. It is partly 
to meet this want that the fermented wort is now added as a part of the 
process. On the other hand, as a compensation for this lack of flavour 
producing changes, the operation is one in which there is no danger of 
those injurious actions occurring of which much has already been said. 
Working with flours that are weak and damp, or even bordering on the 
verge of unsoundness, it is still possible to produce a loaf that should 
be wholesome and palatable, certainly superior to many sodden and 
sour loaves one sees made from low quality flours fermented in the ordi- 
nary manner. In thus stating that it is possible to treat flours of 
inferior quality by this aerating method, the author wishes specially to 
carefully avoid giving the impression that it is the habit of those com- 
panies which work Dauglish's method to make use of only the lower 
qualities of flour ; he has never had any reason whatever for supposing 
such to be the case. His object in the present remarks is simply to 
point out the advantages possessed by this method, should circumstances 
unfortunately arise rendering it necessary to have recourse to inferior 
flours for breadmaking purposes. 

Richardson claims for the aeration process that it is eminently suited 
for the manufacture of whole-meal bread. Of this there is not the 
slightest doubt, whole-meal is not fitted for fermentation processes, and 
the aeration process distends the dough with gas, without the addition 
of any foreign substance whatever. 

It is also claimed for the aeration process that it enables the cerealin 
to be retained within the bread ; and that this is "a most powerful 
agent in promoting the easy and healthy digestion of food." It is stated 
that this agent is retained uninjured by the aerated bread process. The 
author of this statement apparently overlooks the fact that diastasic 
action is destroyed by the subjection of albuminoids to a temperature 
approaching 212° F. However active, therefore, cerealin may be in 
effecting diastasis of starch during panary fermentation, its power is 
destroyed by efficient baking, and the bread contains no active diastasic 
principle. This remark applies with equal force to bread containing 
malt; it is so well known that malt infusion converts starch into 
dextrin and maltose, that from time to time it has been introduced into 
bread. It must here too be remembered that the baking entirely 
destroys its diastasic action, and so causes the malt to be inert as a 
digestive substance. 

422. Gluten Bread. — It is important that the diet of diabetic 
patients should contain no sugar, starch, or other compounds capable of 
being converted into sugar. For their use bread is prepared containing 
the gluten only of the flour. A strong flour should be selected and 
made into a stiff" dough with water only ; this is allowed to stand for 
almost an hour, and then carefully kneaded in small pieces at a time in 
a vessel of water ; the starch escapes and the gluten remains behind. 
Care is necessary in performing this operation, as otherwise the lump of 
dough does not hold together. Should there be any difficulty the dough 
may be enclosed in muslin prior to being kneaded. The gluten must 
be washed in successive waters until it no longer contains starch ; at 
this point the gluten ceases to render the washing water milky. When 



BREADMAKING. 335 



properly washed the gluten is ready for the oven, and is usually baked 
in small rolls or buns ; as it swells enormously during baking a very 
small piece is sufficient for each roll. 

423. Relative Nutritive Values of Different Varieties of 

Bread. — From time to time an agitation crops up in favour of using 
whole-meal for bread instead of finely dressed flour. Yet in spite of 
this the public are found to steadily demand a white loaf. The millers 
who have found themselves, forced at an enormous expense, to revolu- 
tionise the machinery of their mills in order to produce a whiter flour 
are painfully aware of this fact. 

Every baker is familiar with the injurious action of the cerealin of 
the bran during panincation : any reasons which are sufficiently 
powerful to outweigh the disadvantages of this action must indeed be 
cogent. The advocates of whole-meal bread assert that the whole- 
meal is more nutritious than the dressed flour. But this opinion is not 
altogether borne out by facts. Thus, Bell, in " Analysis and Adultera- 
tion of Foods," remarks that — " Contrary to the views sometimes put 
forward by the advocates of the use of wheat-meal bread, the samples 
of household flour submitted to analysis were found richer in nitro- 
genous matter than the entire wheat grains." Whole-meal, however, 
contains a higher proportion of phosphates than does the dressed flour. 
The whole-meal is, of course, the flour plus the bran ; this latter 
substance is rich in albuminoids, but contains no gluten. The bran is 
also rich in phosphates. But from a dietetic point of view, the value of 
an article of food depends not only on its composition, but on what 
substances it yields during the ordinary processes of digestion. In 
chapter XVI., paragraph 361, it is shown that bran yields compara- 
tively little soluble extract to water, so that its actual composition is 
not a fair criterion of what it yields to the human system. Riibner, at 
the Physiological Institute in Munich, made some careful determinations 
of the value of bran as an article of food : by direct experiments on men 
he investigated the amount of material assimilated from three varieties 
of flour; 1, a fine quality ; 2, medium ; 3, flour made from whole-meal 
with the bran. The dough was prepared with pressed yeast. In the 
excreta the following amounts of unused material were found, expressed 
in percentages of the quantity eaten : — 

Variety of Flour. 
No. i. No. 2. No. 3. 

Dry Substance 4-0 6*7 12-3 

Nitrogen 201 24*6 30*5 

Carbohydrates M 2-6 7*4 

The quantity of excreta was high with the whole-meal, the excess 
consisting of the indigestible hull of the grain. Other experiments show 
that the constituents of bran are digested by man only to a very slight 
degree. Further, in an ordinary mixed diet the retention of bran in 
flour is a false economy, as its presence so quickens the peristaltic action 
as to prevent the complete digestion and absorption, not only of the 
albuminoids present in the branny food, but also of other foods taken 
at the same time. Doubtless with the bran ground finer it yields its 
constituents the more readily to digestive action, but the fine bran is 



336 CHEMISTKY OF WHEAT, FLOUR, AND BREAD. 

even more objectionable during panification. The most important loss- 
resulting from the rejection of the bran is that of the phosphates ; this 
loss is however more than made up by the presence of these salts in the 
other food-stuffs of an ordinary mixed diet. The whole of the advan- 
tages of whole-meal bread, without any of its evils, might be obtained 
by the addition of phosphates in appropriate quantity to white flour. 
One argument often adduced in favour of whole-meal bread is, that it 
is specially suitable where little meat is eaten. JSTow in Scotland, the 
people are notoriously little meat eaters ; so also in Ireland the quantity 
of meat eaten is proportionately far less than in England. Yet in both 
these countries the demand is for a white loaf : the Scotch labourer and 
the Irish peasant would reject not merely brown, but also the dirty 
coloured white bread made from low grade flours. 

424. Unsuitability of Barley Meal, <&c, for Breadmaking. 

— Questions often arise as to why barley and other cereals do not make 
such good bread as does wheaten flour. One reason has already been 
given : wheat is distinguished from the other somewhat similar food 
stuffs by its containing gluten ; it is the ' presence of this peculiar albu- 
minous body that confers on wheat flour its characteristic breadmaking 
qualities. The albuminoids of the other cereals, and also of peas and 
the other leguminous seeds, possess more active diastasic properties — 
consequently during fermentation they yield much dextrin, and produce 
dark coloured, sodden, and often sour breads. The diastase of rye is 
particularly active. In addition to the colour produced by diastasis, 
peas have naturally a dark colour of their own, so that their introduc- 
tion into bread would very materially affect the colour. In comparing 
barley and rye flours against that of wheat, the differences in the re- 
spective milling processes must not be ignored. The bran and germ of 
wheat are separated from the flour by most refined methods, while 
barley and rye are still ground, and the meal purified, by the crudest 
appliances. This must of necessity make a difference in the character 
of the flour. 

425. Wheat and Flour Blending. — The consideration of the 

whole problem of blending flours and wheats has been purposely post- 
poned until this stage, in order that the reader may have before him an 
account of the various changes which flour undergoes during the 
operations of panary fermentation. These changes, in short, consist in 
more or less conversion of starch into dextrin and maltose, and in the 
gradual softening and otherwise altering the gluten of the flour. As 
has been previously insisted on, the gluten must have had during fer- 
mentation sufficient opportunity to hydrate and soften sufficiently ; but 
must not have been allowed to further change, as if so it will have lost 
its tenacity, and will produce an inferior loaf. A great deal of the 
success of a skilled baker depends on his having acquired the experience 
which enables him to take his dough and place it in the oven just at 
this right point when fermentation has proceeded sufficiently far to get 
the gluten of the flour in its best possible condition. 

The problem is further complicated by the fact that different flours 
require, in order to arrive at this stage of maturity, different lengths of 



WHEAT AND FLOUR BLENDING. 337 

time in fermentation • hence, as already explained, flours from hard 
wheats are commonly used in the sponge, while those from soft wheats 
are employed in the dough. There can be no doubt whatever that by 
this arrangement far better bread is produced than if the flours be used 
in the reverse order. It is, then, perfectly safe to state that the 
length of time flours require to stand in fermentation is in 
proportion to their hardness or stability. This being the case, the 
question arises as to how this end may best be secured. 

The more advanced bakers demand that the miller shall grind his 
wheats separately, and so enable the baker to mix and blend the flours 
in the manner which suits him best. It is on the face of it evident 
that if a miller mixes hard Indian and soft English wheats together, 
and then mills them, that if each maintains its distinctive character in 
the flour, the gluten of the one must have arrived, during panification, 
at its mature stage long before that of the other. The demand has in 
consequence arisen, that millers shall send into the market straight run 
flours from single wheats. That these are not simply theoretical views 
is shown by the practical fact that this demand for single wheat flours 
is a very real one. American millers are credited with sending to this 
country flours which are made from strictly one wheat only. In con- 
sequence, those millers who are so situated as to feel this competition 
most severely, are now milling and supplying separately straight run 
flours 'Vom Spring American and Winter American wheats. Having 
his single wheat flour, instead of one from what the advanced baker 
views as an incongruous mixture, he uses it at whatever stage of his 
fermentation process that he deems fit. The baker, in being thus able 
to exercise his own judgment, is not handicapped in his efforts to pro- 
duce the best possible loaf of bread from the flour. "With competent- 
bakers, there can be no reasonable doubt that, given flours from 
various wheats, better bread may be obtained when the baker 
judiciously adds the separate flours from the single wheats at 
the proper stage of fermentation, than if he were simply sup- 
plied with one straight-run flour from the whole of the wheats 
mixed before grinding. The first great difficulty here is the 
competent baker : to do his own mixing the average baker requires to 
master principles that at present are almost, if not entirely, unknown 
to him. The author sometime ago urged upon some millers, during the 
course of conversation, that they, instead of making an all-round flour 
by adding some of one wheat for strength, some of another for colour, 
of another for flavour, and so on, should at anyrate divide their wheats 
so as to produce a strong and a weak flour, separate from each other. 
One miller present made the very cogent reply that he had at one time 
attempted this, and had introduced to his customers two varieties of 
flour, the one of which was made from hard strong wheats, the other 
from soft weak ones ; he also made suggestions as to how they should 
be used. On after inquiry he found that, to start with, his flours had 
generally been mixed indifferently with those of other millers, and conse- 
quently any distinctive properties they may have possessed were 
altogether lost. Another objection made by a baker was that he didn't 
want all this trouble of mixing one lot of flour now, and adding another 

w 



d 

•i 

y 



338 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

after : what he required was one good flour, of which he could use one 
part for his sponges and another for his doughs. Coupled with this 
request was the significant hint, that to retain his custom these con- 
ditions must be complied with. Now, evidently, it would have been 
worse than useless for this miller to have attempted to supply single 
wheat flours. There are arguments of the strongest description in 
favour of the baker using a single wheat flour, or at anyrate a flour 
made from closely allied wheats ; but before the miller can advance to 
meet this requirement it is absolutely essential that a sensible proportion 
of bakers, as a class, shall have realised the advantage of working wich 
such flours, and shall have made themselves acquainted with the methods 
of their manipulation. Much good has already been effected by the 
organs of the baking trade in calling attention to the advantages of 
single wheat flours : further benefits will be conferred on bakers by 
these journals in continually supplying practical information as to how 
single wheat flours are best treated, and how superior the results that 
are thus obtained. The author prophesies that when bakers, as a 
whole, are prepared for such a very great change in the system of 
milling in vogue in this country, they will find the millers not 
their natural enemies, but quite prepared to meet their wishes in this 
respect. At present, millers have to deal with the simple fact, that by 
mixing their wheats they can produce a flour from which their baker 
customers can make a fairly good loaf of bread ; whereas, were they to 
supply separate flours from the same wheats milled singly, the majority 
of bakers would totally fail to make an equally good loaf, and the 
miller who was rash enough to make the experiment would find the 
greater part of his trade depart from him. 

In connection with this general question of single wheats versus 
mixtures, there are several points of interest which in passing may be 
mentioned. In the first place, is a straight-run flour from a single 
wheat absolutely uniform within itself 1 Turning back to chapter XVI., 
paragraph 366, an account is there given of the different flours produced 
during gradual reduction. Taking first the Liverpool milled flour from 
a mixture, the flours produced by the earlier breaks, and also the first 
reduction of middlings, were very weak, registering only 60 and 61 
quarts by the viscometer. On the other hand, the flour from the fifth 
break had a strength of 77, and that from the seventh reduction of 
middlings of 75 quarts. Here then is a difference of about 15 quarts 
between the highest and the lowest strength flours produced by gradual 
reduction. The whole of these flours when mixed yielded a straight 
grade flour having a strength of 67 quarts. Similarly with Spring 
American wheat, there is a difference in strength between the weakest 
flour (with 71), and the strongest flour (with 98), of gradual reduction, of 
27 quarts ; the straight grade flour produced at the same time was not 
examined, but in all probability had a strength of about 78 quarts. 
When milling Winter American wheats, the weakest flour had a strength 
of 64, and the strongest, 91 quarts, giving again a difference of 27 quarts. 
There is in each case a difference between the strongest and the weakest 
flours from the same wheat, greater than is observed between any 
ordinary flours sold in British markets. The reason why this difference 



WHEAT AND FLOUR BLENDING. 339 

■exists must be sought for in the fact that the flours come from different 
parts of the wheat grain — consequently we are driven to the conclusion 
that even from one variety of wheat the flours from various parts of 
the grain are not uniform in character. Every single wheat flour is 
therefore of itself a mixture of a number of flours of different strengths. 
Of course different flours may have different strengths, and yet their 
doughs may all fall off in stiffness at about the same rate when allowed 
to stand ; or in other words, their glutens may soften at about the same 
rate. In order to gain information on this point, some stability tests were 
made on the various flours from Spring and Winter American wheats 
already referred to. In order to determine the stability, the doughs, 
after mixing, were allowed to stand for six hours in a water-bath, at a 
temperature of 25° C. (77° F.) ; at the end of this time they were tested 
with the viscometer. The stability figures represent the number of 
quarts per sack the respective flours took in order, after thus standing, 
to make a dough of the standard consistency. The following are the 
results : — 

Strength, 

Spring American Flours — 

Weakest Break Flour 7 1 '0 

Strongest „ „ 72 '0 

Flour from last reduction of Middlings 98*0 
Winter American Flours — 

Weakest Break Flour 64-0 

Strongest ,, ,, ... ... 67 - 5 

Flour from last reduction of Middlings 91*0 

Looking first at the Spring American flours, the two break flours botli 
fall off at the same rate, but the third flour falls off at exactly three 
times the speed. The Winter American flours behave in just the same 
manner, the break flours being very nearly alike, while the middlings 
flour falls off between twice and three times as rapidly as do the others. 
If therefore a straight-run flour from Spring American wheats be taken, 
it is shown to contain within itself flours whose permanence in the 
dough stage differs most widely : the same, too, holds with the different 
constituents of Winter American straight-grade flour. Consequently, 
even with straight-run flours, it cannot be said that they are through- 
out absolutely uniform in their capacity for resistance to the softening 
actions which proceed during panary fermentation. Nevertheless, it 
equally follows that the whole of the flour more closely approaches the 
average, in a single wheat flour, than in a flour from a mixture of 
widely differing wheats. To explain by reference to the flours above 
quoted, the difference between the highest and lowest amount of falling 
off in the various Spring American flours is 9 ; the same figure also 
represents the difference in the case of the Winter American flours. 
But if a mixture of Spring and Winter American wheats were milled, 
the difference between the two extremes would be 1 1 - 5 as against 9 in 
either wheat milled separately. Assuming that absolute uniformity is 
essentially desirable in any one flour, the separate milling of single 
wheats, while not entirely attaining this end, yet approaches more 
nearly to it than the milling of mixtures is likely to do. 



Stability. 


Falling off. 


66-5 


4-5 


67-5 


4-5 


84-5 


13-5 


57-0 


7-0 


61-0 


6-5 


75-0 


16-0 



340 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

In connexion with the same subject, another argument requires con- 
sideration : the action and reaction of different wheats on each other 
while lying together in a mixture is often cited as affording evidence 
having an important bearing on the question of blending wheats. 
Millers frequently state that, if in a mixture, hard-dry Indian and soft 
and comparatively moist English wheats are allowed to lie together for 
some time, they will be found to much more closely approach each other 
in character. The one will have become softer and moister, while the 
other will have become harder and drier. From this it is inferred that 
if the mixture be milled, the particles of flour from each particular 
wheat gradually assimilate in character. But if it can be shown that 
the particles of one and the same wheat, which have been enclosed 
within the same outer coating of bran since the grain had an individual 
existence, do not sufficiently influence each other to render all the 
particles alike in strength and stability, then it is difficult to believe 
that, in grains lying simply side by side, any influence of the one can 
extend to the other sufficiently to effect such an assimilation of the two 
in character, as cannot be produced by the various particles of one 
and the same grain on each other. Considerable interest would attach 
to making such a mixture, allowing it to lie, and then separating the 
two wheats and milling them separately. Such an experiment might 
be made with comparative ease by taking a small grained hard wheat,, 
and a large grained soft wheat : they might then, after lying the re- 
quisite time, be easily separated by a grading or sizing machine. If any 
miller reading this should care to make this part of the experiment,. 
the author will be very pleased to make a series of tests on the flours. 
The probable results would be that while each wheat might be somewhat 
modified, yet it would still retain most of its original character. 

Another question arises — Although the different portions of the 
endosperm, when in situ in the wheat grain, retain distinctive characters, 
may they not rapidly lose these when converted into flour ; and further,, 
would not the flours from different wheats also quickly assimilate in 
character when subjected to intimate admixture 1 That this idea is. 
uppermost in the minds of certain writers on milling questions is shown 
by the fact that the old position is now somewhat dropped, and that it 
is admitted that wheats should be allowed to assimilate before being 
milled. But while any perfect assimilation of wheats is exceedingly 
unlikely, the balance of evidence is also against an admixture of flours 
acquiring uniformity. After mixing, it is, of course, impossible to 
again separate the flours, and test them individually ; but evidence of 
another kind is obtainable. Strong and weak flours have been mixed,, 
and then allowed to stand some time. Such mixtures do not in the 
baker's hands yield such good bread as do the separate flours when 
respectively used in the sponge and dough stage. So far as indirect 
evidence of this kind goes, it is against the theory that flours assimilate 
when allowed to stand together in a mixture. We are consequently 
led to the conclusion that when incongruous wheats are milled together, 
the particles of each retain their respective charcteristics in the flour 
produced, and that when such a flour is fermented one portion arrives 
at the stage of dough maturity considerably earlier than the other. 



WHEAT AND FLOUR BLENDING. 341 



It may be asked, what under such circumstances is the attitude that 
bakers and millers should adopt on this subject 1 So far as the author 
may advise from his standpoint, it is that the bakers should seize every 
opportunity of practically studying the behaviour of single wheat flours 
in the bakehouse ; as they thus get acquainted with their various de- 
meanours, they will be in a position to judge as to how far they may 
advantageously substitute them for flours from mixed wheats. Millers 
will feel the difficulty of absolutely committing themselves to single 
wheat flours to be a very real one. With the different wheats that find 
their way into the corn markets at various seasons of the year, single 
wheat milling would be rendered an expensive operation. In this 
matter, like many others, the question of price is an important factor ; 
it is very doubtful whether bakers generally would be willing to give 
the price for flour that flours from high-class single wheats can command. 
There is, however, one real step in advance that millers might make, 
and that is to mill separately a strong wheat blend and weak wheat 
blend. The incongruity of mixtures of Indian and soft English would 
then be avoided. For the hard wheat mixtures, the various hard wheats 
that come into the market from time to time would be selected, and from 
these a fairly uniform flour for sponging purposes might be made. In the 
same way from the weak wheats a doughing flour might be milled. This 
would be a very near approach to the principle which suggests the use 
of single wheat flours, and would still enable the miller to have a number 
of wheats from which to make his selection. But even this step in 
advance will require for its success the intelligent co-operation of the 
bakers. 

Although not within the scope of this work, it must not be forgotten 
that the question is not purely a scientific one ; it has also an important 
economic side, not only from the narrow view of the purchases of 
individual millers, but also on the broader ground of political economy. 
Further, it should be remembered that those whose capital is involved 
in the purchase of wheat will of necessity have the principal voice in 
deciding whether wheats shall be milled separately or conjointly. It 
is very likely that in the future the problem will be partly solved by 
both milling and baking being performed by the same person to a far 
creater extent than is now the rule. 



342 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



CHAPTER XVIII. 

MODERN BAKING MACHINERY AND APPLIANCES. 

426. Sanitary Considerations. — The operations of kneading 

and working dough involve severe manual labour in a heated atmo- 
sphere : it is impossible to conduct these processes without more or less- 
contamination of the bread with emanations from the skin of the 
workers. In the best conducted bakeries this evil is reduced to a 
minimum by insistance on scrupulous cleanliness on the part of the 
workmen ; still, even the utmost care cannot entirely abolish the evil. 
For the strongest of sanitary reasons, both on behalf of the public and 
of the workmen, operations on dough demand mechanical appliances, 
rather than manual labour. So forcible are these reasons, that the 
expense of kneading machinery and its convenience, compared with 
ordinary manual processes, become merely secondary considerations. 

427. Financial Considerations. — Thanks to the efforts of 

baking engineers, the prime cost of kneading machinery has recently 
been considerably reduced ; so that such appliances can be erected in 
even bakehouses with a comparatively small trade, at no very great 
capital outlay. Against such expenditure must be placed as a set-off,. 
that with the lessening of the amount of manual labour required, the 
bakery staff may be proportionately reduced, or what is the more pro- 
bable alternative, a larger trade will be done with the same staff. As 
the attention of the public becomes more and more directed to the 
hygienic aspect of breadmaking, the demand for machine as against 
hand-made bread is sure to increase : this is a consideration not to be 
lost sight of in comparing the relative advantages of a machine and a 
hand-made bread trade. 

428. Working Considerations. — To those who have been ac- 
customed to work in a particular manner, the revolution in methods 
introduced with machinery, may from simple want of familiarity make 
the more novel processes appear strange and inconvenient. Much of 
this feeling arises from the natural difficulty in overcoming habits of 
long duration. There is often, however, a more serious cause than this 
at work : history repeats itself, and just as hand workers in the past, 
in their ignorance, opposed the introduction of weaving machinery, so 
now, undoubtedly, there is intense prejudice against baking machinery 
in the minds of journeymen bakers. This is unfortunate, for even to> 
the journeyman, the substitution of machinery for hand-labour is an 
advantage, because it makes his work more healthy and less laborious. 
The journeyman's dread is that with a diminution in the amount o£ 



MODERN BAKING MACHINERY AND APPLIANCES. 343 

manual labour required, fewer hands will be employed. But like other 
such changes, this one is not likely to take place with sufficient rapidity 
to sensibly affect the baking labour market : against any such slow 
diminution in the number of bakers employed, the fact must be remem- 
bered that, with the introduction of machinery, the journeyman bakers' 
occupation becomes a more skilled trade. As a consequence his status 
will improve, and his earnings increase : even now a baking foreman, 
who is competent to take charge of machinery, commands higher wages 
than one without such knowledge. Still the fact has to be recognised 
that journeymen generally are averse to the use of machines, and that 
in many cases they wilfully allow dough to spoil that has been machine- 
made in order to show the inferiority of machine to hand work. The 
remedy here is plain : any respectable baking engineer after having 
erected a machine plant will be only too glad to prove its thorough 
efficiency to the master and workmen, by practically showing them how 
to make good bread with it. The proprietor having satisfied himself 
that the machinery is capable of doing its work in accordance with the 
representations of the vendor, should insist on good work being done 
with it. Workmen should be given plainly to understand that, if they 
are incompetent to successfully use the machines entrusted to their care, 
their places will be filled with others who possess the requisite ability. 
It is well known that in Scotland, kneading machines have been ex- 
tensively used for some years : they are there found to answer well and 
to turn out some of the best made bread in the world. 

429. Classification Of Machinery. — The operations of kneading 
and working dough afford the strongest argument in favour of the in- 
troduction of machinery into the bakery ; but with its advent there are 
other purposes to which it can be applied. The principal machines 
employed in a bakehouse are flour sifting machines, sponge stirrers, and 
dough kneading machines. In addition to these, machinery is at times 
used in the manipulation of ferments. Although the oven is not a 
machine in the ordinary sense of the word, the modern improvements 
and inventions in these appliances also merit description. Our present 
work is confined to flour manufacture and breadmaking, but the baker 
who unites confectionery with breadmaking will find, with the introduc- 
tion of a main shaft into his bakehouse, that a number of other minor, 
but most useful machines, can also be driven from it. These include 
currant washers and driers, egg-whisks, and many others. 

The description of biscuit-making machinery lies outside the scope of 
our present work ; otherwise the accounts which follow would naturally 
include detailed references to the well-known and efficient plants 
supplied by T. & T. Yicars, of Seel Street, Liverpool. 

430. Ferment Treating Machinery. — The annexed figure, 

No. 55, represents a combination of machines used for the purpose of 
treating quickly and efficiently large quantities of potato ferment. It 
has been already explained that these ferments require to be cooled as 
rapidly as possible to the fermenting temperature. The first plant of 
this description for bakers' use was made to the order of Mr. Feaist, of 
Hastings. It combines a sifting machine, pump, and refrigerator. 



344 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 




FIG. 55. — FERMENT SIFTER AND REFRIGERATOR. 

The stand on the right hand side of the figure contains both the pump 
and sifter, the boiled potatoes and liquor are poured in at the top ; on 
turning the hook handle shown, the starchy matter of the potatoes is 
worked through the sieve by means of an agitator, which passes to and 
fro immediately above the meshes, the skins remaining on the sieve. 
The pump shown at the bottom right hand corner is worked simulta- 
neously with the agitator of the sieve, and raises the liquid to the top 
of the refrigerator, shown to the left. The refrigerator consists of a 
horizontal series of pipes, through which a current of water can be 
passed. The pump delivers the ferment into a trough at the top of the 
refrigerator, from which it descends as a thin stream over the outside 
of the water pipes, it is again collected at the bottom, and passes in a 
single stream into the ferment tub arranged for its reception. This 
operation serves the double purpose of both rapidly cooling and also 
aerating the ferment, thus ensuring a healthy fermentation. 

431. Flour Sifting Machines. — The object of these is to remove 
any foreign matters, as tyers or pieces of wood, from the flour, by pass- 
ing it through a sieve. Any lumps that may be caused in the flour 
by a sack having been accident ly wetted are also thus separated. 
Sifting also " enlivens " the flour. When flour has been tightly packed 



MODERN BAKING MACHINERY AND APPLIANCES. 345 



in the sacks or bags for some time it forms a compact mass, which mixes 
into the dough with somewhat of difficulty. The passing through a 
sieve divides the flour once more into fine particles, and thus causes it 
to knead all the more easily and readily. It is also very possible that 
the flour thus gets more aerated, and so conveys air into the dough, 
which in its turn acts as a stimulant on the yeast, and so causes more 
energetic fermentation. 

In fixing flour-sifting machines they should be so placed that the only 
passage by which flour can find its way from the flour room to the 
doughing machines is through the sifter. This plan ensures the whole 
of the flour being sifted. 

Descriptions follow of various makers' machines. 

432. Bakers' Flour Sifter. — This machine may be worked either 
by power or by hand ; it may be fixed either on a floor above, or 
immediately over an ordinary doughing trough. Figure 56 gives an 
illustration of this machine fixed in a flour room on an upper floor, and 
leading into a " Thomson " kneading machine beneath. 



346 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 




FIG. 56. — BAKERS' FLOUR SIFTING MACHINE, ARRANGED OVER 
" THOMSON " KNEADER. 



MODERN BAKING MACHINERY AND APPLIANCES. 



347 



The general arrangement of these machines, when actuated by power, 
is here very clearly shown. To the left of the figure may be seen one 
of the hanging brackets, which, depending from the joists of the upper 
floor, carry the driving shaft. From a pulley on this shaft a belt is 
carried to the fast and loose pulleys shown on the right hand side of 
the sifter. It will be noticed that this latter shaft has a crank and 
connecting-rod fixed to the end nearest the observer : this connecting- 
rod gives a reciprocal (forward and backward) motion to an iron 
quadrant, or " agitator," fixed inside the machine. Immediately under- 
neath this quadrant is fixed the wire sieve, shaped to the arc of a circle. 
The machine being set in motion, the flour is tilted in from the sack, as 
shown in the drawing. The agitator moves rapidly to and fro, closely 
above, but without touching the sieve, and in so doing, works the flour 
through the machine with great rapidity. 




348 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



In Figure 57 the same machine is shown arranged to work by hand 
in the flour room, above either kneader or trough. This form is move- 
able, and may be placed immediately on the trough in the bakehouse if 
wished. 

Another advantage of these machines is that, when desired, they very 
thoroughly mix flours. On pouring into the machine, simultaneously, 
flours of two or more different qualities, they are delivered in one 
uniform stream into the doughing machine or trough beneath. 

The makers claim that the sifted flour is doughed in one-third less 
time than with the flour unsifted, and that the sifting is done with a 
speed far greater than had ever previously been attained ; so that the 
operation of sifting, instead of increasing, actually diminishes the time 
necessary for the changing of flour into dough. They also claim that 
the various sizes and forms of their machine enable them to meet not 
only all ordinary, but even exceptional requirements. 

433. Pfleiderer's Flour Sifter. — Like the preceding, this ma- 
chine serves the double purpose of sifting and mixing flour. The 
essential portion of the sifting apparatus consists of a semi-cylindrical 
sieve, above which is fixed a revolving brush. The bristles of this 
brush are arranged in a spiral or screw-fashion around its axle : as the 
brush revolves, the bristles rub against the sieve with a motion com- 
pounded of that resulting from the rotation of the brush and an onward 
movement from one end to the other, due to their spiral setting. In 
this manner the flour is forced through the sieve at a rate, it is stated, 
of a sack per forty to sixty seconds, according to the mesh of the sieve, 
the size of the sifter, and the speed at which it is worked. 




FIG. 58. — SECTIONAL VIEWS OF PFLEIDERER*S FLOUR SIFTER. 

Figure 58 shows two sectional views of this flour sifter, the one being 
longitudinal, and the other transverse. The general arrangement of 
the revolving brush and other parts of the machine are clearly illus- 
trated. 



MODERN BAKING MACHINERY AND APPLIANCES. 349 



FIG. 59. — PFLEIDERER'S FLOUR SIFTER FIXED UNDER FLOOR. 

This figure gives an illustration of the external appearance of the 
same machine, fixed below the floor of flour room, and arranged so as 
to deliver into either kneader or trough placed beneath. 

434. Sponge Stirrers. — In Scotland, it has been the custom to 
set sponges in large tubs : a machine, termed a " sponge stirrer," has 
been devised for the purpose of rapidly mixing the barm, flour, and 
water together. The principal portion of the machine is a vertical 
spindle, so fixed that it can readily be lowered into the tub, placed to 
receive it : the lower end of the spindle is provided with a point and 
shoulder which rest in a socket fixed in the bottom of the tub. The 
spindle is balanced by a weight attached to the one end of a chain which 
passes over a pulley and is fastened to the top of the spindle. The 
machine is driven by mears of a belt-pulley and bevil gearing. A 
number of horizontal blades, fixed to the lower portion of the spindle, 
by revolving in the tub, speedily ensure the efficient stirring of the 
sponge. 

These machines do not now seem to be used to so large an extent as 
formerly : bakers, who have kneading machines, now frequently prefer 
to set the sponges in the machine. 

435. Kneading Machines. — Several highly successful machines 
for doughing and kneading purposes are now in the market. Among 
the best known are those of Pfleiderer, Thomson, and Melvin. These 
have been selected as examples for description. 

436. Pfleiderer's Doughing Machine. — All doughing machines 

consist essentially of a trough, usually made of iron, in which the flour 
and water are placed. One or more sets of blades revolve in this trough, 
and in so doing, knead the flour and water into dough. 

The reader is in the first place referred to Figure 60, in which the 
arrangements of these blades in the trough is well shown. This figure 
is drawn from a small working model of the Pfleiderer machine, such as 
the author uses in doughing experiments with the strength burette and 
the viscometer. Attention is called to the two revolving kneaders, the 



350 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



axes of which are separate and parallel to each other. These kneaders 
are geared together by means of toothed wheels : an essential point 
about these wheels is that they have different numbers of teeth, and so 
the two shafts revolve at unequal rates. 




FIG. 60. — WORKING MODEL OF PFLEIDERER's DOUGH MIXER. 

In order to show the blades more clearly, the upper part of the trough 
Jias been removed. This particular machine is worked by a hook handle 
placed on the square end of either of the axes. 




FIG, 6l. — PFLEIDERER'S DOUGHING MACHINE IN KNEADING POSITION. 

Turning next to the machines of sufficiently large dimensions for 



MODERN BAKING MACHINERY AND APPLIANCES. 



351 



bakehouse use, an illustration of one of these is given in Figure 61. 
Figure 62 is also a view of the same machine uptilted so as to turn out the 
finished dough into a trough that may be placed in order to receive it. 
At the right-hand side of the machine are two pulleys, C.C. ; one of 
these is driven by an ordinary, the other by a crossed belt, from the 
same driving shaft. By putting either one or the other of these pulleys 
into gear the machine may be caused to revolve in either direction. 

The starting, stopping, or reversing of this machine is effected in an 
exceedingly simple manner. On the same shaft as the pulleys C.C. is a 
hand-wheel with a smooth rim. The machine is so devised that it pre- 
cisely obeys all the motions of this wheel ; thus, when the machine is at 
rest, if the hand-wheel be turned either way, the machine im- 
mediately follows suit, by revolving in the same direction. When the 
machine is in motion, if the hand-wheel be stopped, by grasping the rim, 
the machine also stops. The lever F, to be worked by the foot, tilts 
the machine when required. The tilting does not interfere with the 
working, as the blades may still be caused to revolve in either 
direction, with the machine uptilted. At the back are shown two 
weights, P.P., by which the machine is balanced, rendering it extremely 
•easy to turn it over when desired at the close of the doughing operation. 
One special feature of this form of the machine is its being set very 
low. It will be seen that when in the working position, the top of the 
trough is barely breast high. 




FIG. 62. — PFLEIDERER'S DOUGHING MACHINE, TILTED FOR DISCHARGE. 



352 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

In Fig. 62, the position of the blades D.D. is clearly shown : in 
general configuration they resemble those of the smaller machine in 
Fig. 60. The foregoing brief description, together with a study of the 
engravings, will render clear the more important points of construction 
of these machines. 

In making dough the flour is first inserted, and then the requisite 
quantity of water ; the blades are in the first place caused to revolve,, 
so that at the top of the revolution they approach each other. The 
machine works best with just sufficient flour to entirely cover the blades 
before the mixing commences. An endeavour must now be made to 
describe the results produced by the movement of the blades ; this is a 
matter of some difficulty. It should be mentioned that the trough of 
the machine is so shaped that the blades in the course of their revolu- 
tion scrape it quite clean, no lodgement for the dough being permitted 
in any part. The blades bring the flour and water continually from the 
sides of the trough toward the centre, and there mix them together ; 
they then pass down through the centre, and at the bottom of the trough 
are separated into two portions ; one of each is again brought to the 
surface by each blade traversing the circumference of the trough in its 
passage. Following the one portion only, it is with the completion of 
the revolution brought once more to the position where the two blades 
meet; but as the one blade is revolving more quickly than the other, the- 
two portions which were separated as the blades descended do not again 
come in contact, each one is mixed with a fresh portion of the dough.. 
This differential motion is one of the most important features of the 
machine, and effects the thorough mixing of flour and water with great 
rapidity. A very few turns of the machine changes the loose flour into 
tough plastic masses of dough ; the action of mixing at that stage re- 
solves itself into the pressing together of the portions of dough, cutting 
it asunder in fresh places and again reuniting. After some little time it 
is well to reverse the motion of the machine for a few revolutions. As 
soon as the kneading is completed the machine is turned over in the 
position shown in figure 62 ; the mechanical arrangements are 
so adjusted that this operation does not interfere in the slightest with 
the revolution of the blades. These should then be reversed, when 
they discharge the dough with the greatest readiness. 

Great care and thought have been exercised in devising the shape and 
arrangement given to these blades. The object is to secure the most 
efficient possible mixing, with the least possible cutting and dividing of 
the dough. 

This machine is made in a number of sizes, and may be obtained to- 
work either by hand or by power : the former source of power is 
obviously only applicable to the smaller types of machines. When 
specially wished, the machine is supplied with a steam jacket, by means 
of which it can be warmed before use. 

The makers claim for it that it is equally applicable to the mixing of 
dough of any required degree of stiffness, whether for bread, cake, or 
biscuits : that it is exceedingly strongly made, and will stand con- 
siderable rough usage without serious injury, although, of course, such 
treatment is to be deprecated. The bearings of the shafts are so con- 



MODERN BAKING MACHINERY AND APPLIANCES. 



353 



structed as to absolutely prevent any oil or lubricating material entering 
the dough. While the machine is admirably fitted for thoroughly 
kneading and mixing dough, its peculiar construction enables it to 
discharge the finished dough with the greatest readiness, and so 
thoroughly that there is not the slightest waste. 

For further information the reader is referred to the makers of the 
machine. 

437. The " Thomson " Kneading Machine.— An end view of 

this machine, together with Hour sifter, is shown in Figure 56. The 
machine consists essentially of an iron trough, which is usually gal- 
vanised, and in which revolve two kneading arms, whose arrangement 
is shown in the following figures, Nos. 63 and 64, which give longitu- 
dinal and transverse sections through the machine. 




354 



CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 




FIG. 64. — TRANSVERSE SECTION THROUGH THOMSON KNEADING MACHINE. 

The lettering throughout these two figures is the same. The outer 
kneader, marked a b c in figure 63, is so shaped as to adapt itself closely 
to the semi-circular bottom of the trough, within which it revolves as 
nearly as possible to the surface without touching. As shown in 
transverse section at c, the metal of this arm is about three-quarters of 
an inch in thickness, and is of uniform dimensions from end to end ; so 
far, therefore, this kneader would, when revolving, pass knife-like around 
between the dough and the trough, doing little or no work upon the 
former. But from the inner surface of c there projects at right angles 
to it a series of blades, e e, each of which is set obliquely on c. The 
second kneader, g h i, revolves within a b c on the same centre, i ; from 
g h there projects inward a series of blades,^'/, and outwards another 
series, h h. The blades, e e, of the outer kneader interlace in working 
with the blades, k Jc, of the inner kneader. The whole of the blades of 
these series are set obliquely to the direction in which they meet the 
dough. These kneaders revolve independently of one another, and are 
capable of the following motions — 1st, either may be set at work with the 
other remaining at rest ; 2nd, they may be caused to revolve in opposite 
directions, when, by differential gearing, the one rotates more rapidly 
than the other, and so the two meet with each successive revolution at 
different points ; 3rd, the two may be locked together at any angle, and 
caused to revolve as though they were one. By means of special 
gearing a fast and slow speed is provided, so that as the dough becomes 
stiffer and offers more resistance, greater force can be exerted by re- 
ducing the speed of revolution. 



MODERN BAKING MACHINERY AND APPLIANCES. 



355 



A glance must now be taken at the outer gear of the machine : on its 
main shaft at v, figure 63, are fixed three pulleys — one, the middle one, 
being loose, and the other two fast. These provide for the machine 
being at rest, or for its revolution in opposite directions. The small 
pinions, q r s t, constitute the gear, by which a slow motion is obtained 
when required. The inner kneader, g h i, is driven by the toothed 
wheel, while the outer kneader, a b c, is attached to a sleeve, m m, 
which encircles the shaft o, and is driven by the wheel n. The rod, y y, 
at the lower part of figure 63, is a part of the reversing gear. This is 
seen more clearly in the transverse section, figure 64, this rod is there 
shown to be connected to a handle, marked also y; to this handle is 
attached a locking spring, I. By placing the hand upon this lever 
handle and moving it into either of three set locks, the several move- 
ments of which the machine is capable are obtained. The different 
positions in which the kneaders are, when these changes are made, 
cause the many varied actions that can be given to the dough. Another 
lever works the fast or slow speed, or loose stop pulley. The handle, 
w, figure 64, is for the purpose of tilting the machine. 

The makers claim that, by means of this machine, they obtain 
jziowerful mixing motions, which have a real kneading action, corres- 
ponding to the pressure of the hand or arm, and allowing the dough to 
have relief or spring ; also, that the machine works with a low driving 
power, and discharges its contents at the finish more easily and cleanly 
than from an ordinary bakers' trough. They further claim that their 
machine, while kneading the dough in the shortest possible time, is so 
devised as to reduce the danger of damage to the dough, as a result of 
overworking, to a minimum. 

438. Melvin's Kneading Machine. — As in other machines, 

the trough is adapted in shape to the revolving kneaders, of which, in 
Melvin's machine, there are three, set on separate shafts. 




FIG. 65.— MELVIN'S DOUGH MIXER. 



356 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



Figure 65 illustrates the external appearance of this machine. Its 
interior is shown in Figure 66, from which it may be seen that there are 
three actions, each action being represented by a separate set of blades, 
which receive motion at each end of the machine by means of gearing. 




FIG. 66. — SECTION THROUGH MELVIN'S MACHINE. 

The three radii described by the several sets of blades in their rota- 
tion all intersect one another, so as to prevent there being any dead 
centres in the mass of dough. Their rotative action is such that there 
is a continuous overlapping movement of one set over the other, above 
the central line of the axes of the machine. At the latter point the 
blades pass each other in opposite directions, side by side, and at the 
bottom of the machine they pass obliquely to each other. These actions 
produce the following effects on the dough, viz. : the whole top surface 
of dough is raised into folds, which are thrown the one on the top of the 
other, and then drawn downward into the centre of the mass. While 
this is being done, the outer portions are carried upwards by the two 
outside sets of blades, to be in their turn folded and carried downwards 
at the centre. The blades, where they pass in the centre, have a cutting 
or dividing action, and at the bottom they have a pressing action. The 
overlapping movement constitutes the kneading process, while the cut- 
ting and pressing mixes. The dough is discharged by tilting over the 
trough by worm gearing, worked by a handle at the side. The maker 
claims that all these actions are necessary essentials in the making of 
good dough. 

439. The "Drum" Dough-Kneading Machine. —This 

machine has been recently introduced by Baker & Sons. The mixing. 
receptacle consists of a drum or cylinder fixed horizontally. 



MODERN BAKING MACHINERY AND APPLIANCES. 



357 




Through the right hand end of the drum, as shown in figure 67, 
passes a horizontal spindle carrying one kneading arm, which is just 
visible through the partly open door at the left hand, or outside end of 
the drum. In use, this end door is closed, the flour and water are then 
introduced through the door fixed on the top of the cylinder, and shown 
in the figure. The kneading arm is then caused to revolve, and in so 
doing is also made to travel longitudinally from the one end of the 
cylinder to the other. When the dough is sufficiently kneaded the end 
door is opened, and the kneader, in working, discharges the dough 
through this from the cylinder. 

The makers claim that with only one kneading arm, instead of several, 
there is a great reduction in the amount of power required ; that at the 
close of the doughing operation, the kneading arm being to the front, 
the machine can be easily cleaned. They specially recommend it for 



358 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

adoption in small bakeries, where all machinery is driven by hand, or 
where only a very small engine is employed as the source of power. 

440. Killing or Felling of Dough. — Discussions occur from 
time to time as to whether doughing machines kill or otherwise injure 
dough. As a result of careful experiments the author is of opinion 
that it is possible to injure dough by overhneading it in a machine. 
The tenacity of dough may be sensibly reduced by too much kneading ; 
or, in other words, a stiff dough can be reduced by overkneading to the 
consistency of a dough originally made much slacker. Be it noticed 
that this is a result of overkneading, not of proper kneading. A batch 
of dough, which by hand requires, say, twenty minutes to knead 
properly, can be sufficiently kneaded in the machine in, say, four 
minutes. Now, if by hand-work the dough receives a minute's too 
much kneading, that is only an excess of five per cent, on the proper 
time ; but a minute's overkneading in the machine means twenty-five 
per cent, excess over the proper time. The minute in the one case is 
five times more serious an error than in the other. Besides, the baker 
working by hand knows by the feel of his dough when it is sufficiently 
kneaded ; and with the machine he has to judge in a different manner. 
It is so much easier work, too, to watch the machine overkneading a 
sample of dough than to do it one's self. The remedy for this evil is to 
drive the machine not too quickly, and to stop working immediately 
the dough is sufficiently kneaded. The necessary time may be ascer- 
tained very closely once and for all by a careful experiment made with 
the machine. It is a compliment to the makers of doughing machines 
generally, that the principal complaint against them is not that they 
are inefficient, but that they are liable in a very short time to do their 
work too thoroughly. The remedy for this fault is simple and obvious. 

441. Cleaning Doughing Machines. — It is essential that these 

machines be kept perfectly clean : each day after using, every fragment 
of dough should be removed, and the machine scraped and wiped out. 
The machine being absolutely clean it is a very good plan to wipe its 
interior with some clean waste and best cotton oil. This is quite 
tasteless, and the oily film causes the dough to leave the machine more 
completely. 

442. Ovens. — The space at disposal renders it impossible to give 
more than a brief account of ovens ; a few typical ones of modern make 
have been selected for description. 

443. The Bailey-Baker Oven.— This oven is fired by an exter- 
nal furnace, so arranged that the heated products of combustion lead 
directly into the oven. An idea of its construction may be gained from 
a study of the accompanying illustration, Figure 68, which gives a 
longitudinal section. 



MODERN BAKING MACHINERY AND APPLIANCES. 



359 




FIG. 68, — BAILEY-BAKER OVEN, LONGITUDINAL SECTION, 

Starting from the front of the oven at the floor-line, there is first the 
ash-pit : above this is the furnace, extending about two-fifths of the 
length of the oven. From this it will be seen that the furnace is 



360 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

arranged at the front, but if desired, the makers place the furnace 
either at the back or side of the oven. From the furnace two flues 
start, one from either side, and communicate with the two front corners 
of the oven's interior. Another flue proceeds to the back of the oven, 
and subdivides so as to discharge into its two back corners. These flues 
provide for the heating of the oven by the admission of the heated gases 
from the furnace simultaneously at the four corners : in order to provide 
for the maintenance of a draught through the oven, a main exit flue 
leads from immediately above the oven door to the chimney. There is 
also provided a flue leading direct from the furnace to the chimney, so 
that any momentary slight smoke or dust caused by the addition of 
fresh fuel to the furnace need not be admitted to the oven. Another 
flue to which the inventors attach considerable importance, and which 
they term the " siphon " flue, leaves the oven from the middle of one of 
its sides, close to the crown, takes a downward path until considerably 
below the sole of the oven, then bends forwards and upwards toward the 
main flue, into which it enters above the damper. The object of this 
flue is to permit the slow escape of gas without loss of heat. All the 
flues are provided with dampers, so that, at the discretion of the baker, 
all or any may be opened or shut at will. Reference to the illustration 
shows that there is a space between the sole of the oven and the 
crown of the furnace : this constitutes a hot-air chamber, which at the 
back communicates with the interior of the oven. 

This oven is specially designed for use with coke or hard smokeless 
coal (anthracite), of which the inventors state (referring to the coke), a 
sack per twenty-four hours is required. The heat of the oven may be 
regulated with extreme nicety by opening or closing the ashpit door, as 
with the open door more rapid combustion goes on in the furnace. By 
means of the dampers the hot-air from the furnace can be directed 
through the flues described into the oven at all or any of the four 
corners, thus raising its temperature to baking heat with great rapidity. 
These arrangements permit the baker to first thoroughly heat his oven, 
and then, closing the dampers, to conduct the baking of his bread by 
" solid " or radiant heat in a closed oven : he may then at will admit a 
flash heat so as give a " bloom " to the crust. During the time that the 
oven is closed, the heat of the furnace raises the temperature of the air 
in the hot-air chamber beneath the sole: this hot-air by convection finds 
its way all over the oven, and so serves to raise the temperature through- 
out equably and gently. The inventors claim that in this manner the 
oven can, if wished, be made to bake entirely by external heat. 

The makers and inventors claim for this oven that the greatest possi- 
ble quantity of all the heat produced is used, so that the cost of fuel is 
reduced to the lowest practicable amount ; that as no firing is done 
within the oven no scuffling is required, as the interior of the oven is 
free from dust and ashes. That there is absolute control over the oven, 
thus permitting the baker to use more or less heat as he requires, and to 
direct it to whatever part of the oven he wishes : further, that he may 
have either a solid or a flash heat at will. That batch after batch may 
be baked continuously, and with perfect regularity of production. That 
when the oven is required at a low temperature for the baking of certain 



MODERN BAKING MACHINERY AND APPLIANCES. 



361 



goods, the change can be effected in very little time, and that as soon as 
desired the oven can again be raised to the normal temperature with 
great rapidity. 

444. The "Mason" Continuous Baking Hot-Air Oven. 

— This oven may be made either Single or Two-Decker; the latter term 
signifying that the one oven is placed immediately above the other. 
They are heated by a furnace at the base, which can be placed on any 
side of the structure, but by preference at the back, so that all dust and 
ashes may be kept out of the bakehouse. When wished, these ovens 
can be supplied fitted with travelling plates, enabling the whole of the 
batch to be set or drawn at once, and thus securing uniformity of colour 
and baking. In the two-decker the tram-lines for the travelling plates 
are so arranged that they can instantly be transferred from the top to 
the bottom oven, and vice versa, as required. The accompanying illus- 
tration, Figure 69, gives a longitudinal section through the two- 
-decker oven. 




FIG. 69. — LONGITUDINAL SECTION THROUGH " MASON " TWO-DECKER OVEN. 

Referring to the Figure, it will be seen that the furnace is at the back 
of the ovens and is so arranged as to be quite independent of them. In 
order to prevent direct radiation of heat from the furnace chamber 
through the back of the oven, a cold-air chamber is placed between : as 
a result of this arrangement the inventor states that it is possible to 
lieep the back of the oven at a lower temperature than is the front. 
Further reference to the Figure shows that the heated gases pass from 
the furnace chamber through a main flue, and first come into contact 
with the oven-sole at the front, and then pass to the back of the oven, 
and from thence between the crown of the lower and the sole of the 
upper oven : continuing their course, the heated gases next pass over the 
top of the higher oven and from thence to the chimney. By means of 
•dampers and special arrangements of the flues the heat may, when it is 
.desired, be applied to both top and bottom of each oven, or to either 



362 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



top or bottom only, or the heat may be directed straight up the chimney. 
In this way the heat of the oven is kept under direct control of the 
baker. As the oven is entirely heated externally, it is absolutely 
impossible for any dust or smoke whatever to find its way from the fur- 
nace to the oven. From the cleanliness point of view it is a very great 
advantage to have the oven furnace outside the bakehouse, and thus to 
do entirely away with the introduction of coal and ashes into the 
bakehouse itself. 

The inventor and patentee claims that this oven has its greatest heat 
at the front of the oven, where it is most required, that the temperature 
is under complete control, and that the baker can apply heat to either the 
crown or sole of the oven as he may wish. That the only part of the 
oven liable to repair is the furnace chamber, which is easily accessible, 
and that there is no destruction going on within the ovens themselves. 
That the oven being heated from the outside, no dust or ashes are intro- 
duced in the bakehouse. That the consumption of fuel is very small, 
and that no more is required for a two-decker than a single oven. 

445. Steam Ovens. — One of the most interesting points about 
these ovens is that they are not heated either externally or internally by 
the direct heat of the furnace itself, but that the furnace converts a 
quantity of water, contained in hermetically sealed iron tubes, into 
superheated steam. These tubes in their turn radiate heat into the oven. 

It is well known that when water is boiled at atmospheric pressure 
the temperature of the steam is 212° F. (100° C), but when the steam 
is confined so that the pressure may increase, the boiling point of the 
water and of the steam produced rise to a height determined only by 
the temperature of the furnace and the limit of resistance of the boiling 
vessel. Thus the boiling point of water at a pressure of 420 lbs. per 
square inch is 447*6° F. (230-9° C.) 




LINE" 






FIG. 70. — PERKIN'S STEAM OVEN — LONGITUDINAL SECTION. 

The above is an illustration of Perkin's steam oven, this firm being: 
the original patentees of the principle of applying superheated steam ta 



MODERN BAKING MACHINERY AND APPLIANCES. 



363 



the heating: of ovens. Reference to the illustration shows that the oven 
is fired at the back, thus keeping the bakehouse free from coal and 
ashes. A back view of the oven is given in the following figure, No. 71, 




FIG. 71. — BACK VIEW OF PERKIN'S STEAM OVEN. 

These diagrams are self-explanatory, so far as the furnace, ashpit, and 
their fitttngs are concerned. An air-chamber is fixed between the 
furnace and back of the oven, so as to prevent the oven being over- 
heated at the back by the direct heat of the furnace. From the furnace 
two parallel series of pipes proceed ; these are arranged, the one series 
underneath the bread plate or sole, the other just below the crown of 
the oven. These pipes are made of iron, each being complete in itself, 
and having an external diameter of If inch, and internal diameter of 
■| inch, leaving -| inch as the actual thickness of the metal. They are 
tested at a pressure of 3000 lbs. per square inch. Before being closed 
each pipe is partly filled with water ; with the heat of the furnace this 
water is converted into superheated steam, and so, by proper regulation 
of the heat, each pipe is raised throughout to a temperature of from 
450° to 500° F., thus giving the oven an equable solid, or radiant, 
baking heat. A flue, fitted just inside the oven door, is provided for 
the escape of steam during baking ; this may be opened or closed by 
means of a damper. It must be clearly understood that this flue simply 
provides for the escape of steam evolved from the bread, not for any 
escape from the steam pipes of the oven. These latter being once filled 
and sealed up require no further treatment until worn out. 

As this oven is entirely closed off from the furnace it is impossible 
for any dust or fumes from the fire to find their way inside : on the 
other hand, it follows that the goods cannot be subjected to a flash 
heat. The oven is exceedingly simple in construction, but its initial 
cost is great, through the expense of the iron-work. 

Nevill, the well-known London baker, employs steam ovens on a 
slightly different principle : his are arranged so that the pipes are 
heated by the circulation of a current of steam through the whole series. 
The advantage of having each pipe distinct from the others is that 



364 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



should one become leaky and disabled it does not interfere with the 
proper working of the others. 

446. Thompson's Gas Oven — This oven is a fresh departure 
from those previously described, inasmuch as gas is used as fuel instead 
of either coal or coke. .Thompson Bros, supply this oven in small sizes, 
in which the whole oven, together with heating appliances, is self- 
contained, and is portable ; and also supply ordinary bakers' ovens, 
fitted with gas-heating apparatus. The accompanying illustration 
shows a front view of the bakers' oven. 




fig. 72. — Thompson's gas-heated bakers' oven. 

These ovens are brick and tile built, and are heated by gas on the 
regenerative principle ; that is, the waste heat from the oven is 
employed to heat the gas and air, used for supporting combustion, prior 
to their reaching the burners. This is effected by causing the pipes 
bringing gas and air to the flame to pass through the flue, conveying 
away the products of combustion. The makers apply the heat either 
externally or internally as desired, but find that internal heating is 
most generally favoured, as by means of gas a flash heat is obtained in 
the cleanest possible manner, as no smoke, soot, nor ashes are produced. 
A series of bunsen (atmospheric) burners is placed on each side of the 
door inside the oven, and are regulated by taps on the outside. The 
heated products of combustion from these burners are carried to the 
back of the oven, and return underneath the oven sole to the front, and 
thence into the main flue. By this means not only is the inside of the 
oven heated, but underneath also, thus ensuring both top and bottom 
heat. When desired for special purposes the oven is supplied with 
arrangements for the production of additional bottom heat. 

The externally heated oven is supplied with a heating chamber 
placed underneath the front of the oven : the heat is conveyed under- 



MODERN BAKING MACHINERY AND APPLIANCES. 



365 



neath the oven sole, up flues at the back, and returned inside cast-iron 
flues to the front, and thence into the main flues. 

The manipulation of the heating arrangement is very simple ; the pro- 
per way is to open the dampers before lighting the gas, and to close them 
immediately after the gas is turned off" : by carefully attending to these 
points it is impossible to have a failure. 

The makers claim that their system of gas heating gives cleanliness, 
uniformity of heat, simplicity in firing, freedom from sulphur, smoke, 
and ashes, and retention of heat. There is also a considerable reduction 
in labour required. It is further claimed that the cost of heating is less 
than that for coal ; in support of this claim the makers adduce the 
Official Report of the Testing Engineer of the Gas Exhibition held at 
the Crystal Palace, 1883 ; and also testimonials from well-known firms, 
who state the cost of heating to be nominal. 

447. Baker's Patent Oven Light. — This is an apparatus ar- 
ranged for the purpose of lighting the interior of an oven, not only 
while the bread is being set, but also at will while baking is proceeding. 




FIG. 73. — BAKERS OVEN LIGHT. 

The apparatus consists externally of an iron box so arranged as to be 
fitted into the wall of any baker's oven. The gas jet is fixed in a lantern 
with a semi-circular mica face, and a reflector behind. When not in 
use, this lantern remains withdrawn into the upper portion of the box ; 
the opening being closed by a small iron door, shown in the figure just 
to the left of the light. On turning over the weighted handle, on the 
outside of the apparatus, the iron door is opened, the light is turned 
full into the oven, and at the same time the gas is turned full on. The 
reverse movement again withdraws the light, turns the gas down, and 
shuts the iron door opening from the light-box into the oven. The light 
can in this way be projected into the oven during the time that a batch 



366 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

is being baked. By having a small window of glass fixed in the oven 
door the interior can thus be inspected without opening the oven. 

The makers claim the saving of gas with this light is very great, as 
the gas is turned down automatically when the light is not in use. The 
loss of heat and steam caused by opening the oven door in order to see 
the interior is entirely avoided. The light is ventilated, so that it is 
not affected by the heat or steam, and the whole interior of the largest 
oven is brilliantly illuminated. 

448. The Author's Personal Opinions on Ovens and 

Machines. — In writing the preceding descriptions it has been the 
author's aim to impartially describe each particular machine or appliance 
referred to, giving that information which was deemed most likely to be 
of interest to the baker, who would wish to know something of the 
objects and nature of kneaders and ovens, &c, of comparatively modern 
invention. In order that no special point of merit of any system shall 
be overlooked he has asked the various makers to supply him with 
particulars of whatever special advantages they claim. These have been 
incorporated in the descriptions, but in such a way as to separate the 
makers' claims from purely descriptive matter. The author has carefully 
avoided indicating any preferences whatever of his own ; those readers 
who desire his personal opinions or advice as to the selection of ovens 
and machinery may obtain the same by consulting him professionally. 



ANALYTIC APPARATUS. 367 



CHAPTER XIX. 

ANALYTIC APPARATUS. 

449. Commercial Testing and Chemical Analysis of 

Wheats and Flours. — The remaining portion of this work will be 
devoted to practical directions for testing and examining wheats and 
flours. As a matter of convenience, the various analytic operations are 
divided into two classes ; first, those which are more readily performed, 
and which afford information having the most immediate bearing on the 
actual value of wheats and flours ; and second, those determinations 
which are more purely chemical in their nature. The operations of the 
first class are comprised under the heading of " Commercial Testing of 
Wheats and Flours ; " their nature is such that they may be performed 
personally either by the miller or baker. The second series of tests 
requires rather more chemical knowledge and experience : they conse- 
quently appeal more particularly to the students of milling and baking 
who have had the advantage of a course of chemical training in a pro- 
perly appointed laboratory. The matter of the succeeding chapters has 
already in another form been largely used by such students of the 
author's as their practical text-book in the laboratory. It is also hoped 
that a knowledge of how the operations of chemical analysis are con- 
ducted will be of interest to other readers who may not have the time 
or opportunity of themselves going personally over the practical work. 
The chief reason why millers and bakers should understand analytic 
methods is not that they will continually be practising them in after 
life, but that they will often wish to make themselves acquainted with 
the results obtained by scientists and their deductions therefrom. These 
results can only be fully understood and their exact bearing appreciated 
by those who are familiar with the methods by means of which the 
results are attained. 

A description of the laboratory and of the principal analytic appa- 
ratus used in weighing and measuring will now be given as an intro- 
duction to analysis. 

450. The Laboratory. — For the benefit of any millers and 
bakers who may wish to fit up a laboratory for themselves, the following 
few hints as to utilising a room for the purpose are here inserted. If 
any work is to be done beyond the roughest experiments, a balance 
and microscope will be requisite ; these delicate instruments must be 
kept free from dust, and so cannot be exposed to the ordinary atmos- 
phere of the mill ; they should, therefore, be placed in either a private 
office or study, and covered over when not in use. For the other pur- 



368 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

poses of a chemical laboratory, almost any room, or part of a room, can. 
be made to answer. A working bench or table should be fitted in as 
good a light as possible, at a convenient height. Gas, when obtainable, 
should be laid on to this bench by means of a pipe terminating in a 
nozzle, over which a piece of india-rubber tubing can be slipped. There 
should be near at hand a drain, over which is fixed a tap, with a good 
water supply. This tap should also have a small side tap, with nozzle 
for india-rubber tubing, in order to lead water into any apparatus in 
which it is required. These are almost the whole of the necessary 
fixings. There must, of course, be a few shelves on which bottles and 
the various apparatus may be kept. With time, and money to spare,, 
many additional fittings might be suggested. These can, if wished,, 
be added afterward. 

451. The Analytical Balance. — It is presumed that the student 
will have, before attempting the following work, made himself familiar 
with the simpler chemical apparatus, by their actual use in the 
laboratory. Quantitative analysis, as its name implies, is that species 
of analysis by means of which the quantity or amount of each ingredient 
in any particular body is determined. For purposes of analysis, quantity 
is measured and expressed either by weight or by volume. Accordingly,, 
the chemist first of all requires some accurate means of determining. 
with exactness both weight and volume. 

For purposes of weighing, an accurate balance and set of weights are 
necessary. Of these there should be in a laboratory at least three of 
different degrees of sensibility. Taking the most delicate first, let us- 
describe what may be termed the " analytic balance proper." This 
instrument requires to be made with the utmost care and accuracy — 
the figure given is an illustration of an analytical balance made by 
Mr. O. Wolters, -of 55, Upper Marylebone Street, Portland Place, "W, 
The speciality of this particular variety of balance is that the beam is 
very short ; the maker claims for it that, as a result, the delicacy of 
the balance is increased, while the time in which a weighing is performed 
is lessened. The writer has had one of these balances in use for some 
time, and is able to speak well of them from practical experience. 



ANALYTIC APPARATUS. 



369 




SHORT BEAMED ANALYTICAL BALANCE. 



On referring to the figure it will be noticed that the balance is 
enclosed in a case ; the bottom of this consists of a stout slab of glass, 
fixed on levelling screws, b b. The front, back, and sides of the case are 
glazed ; and all open, the front and back by sliding up, the two sides on 
hinges, as doors. The beam is suspended on a brass pillar, which in 
turn is screwed down to the botttom of the case. The beam carries at 
its centre a knife-edge made of agate, this rests on a plane of the same 
material ; on each end of the beam there are similar knife-edges, and 
from these depend the scale pans. When the balance is not in use the 
beam, instead of bearing its weight on the knife-edge, rests on a sort of 
cradle, d d : so, too, the end hooks carrying the pans are likewise sup- 
ported by the cradle. Underneath each pan there is also a small ivory 
support, on which the pans rest until it is required to set the balance in 
action. At the bottom of the left-hand side of the figure will be noticed 
a small handle, a ; this, on being slowly turned from the operator, first 
lowers the ivory supports from beneath the pans, then drops one portion 
of the cradle, and so suspends each scale pan from the terminal knife- 
edges of the beam, and next lowers the central knife-edge on to its agate 
plane, and permits the balance to swing. On turning the handle back 
again, the opposite of these movements takes place in reverse order, and 
each knife-edge is gently lifted from the agate plane. The object of 
this is to prevent wear of the edges by their being continually in con- 
tact, particularly as a balance would soon be seriously injured by the 
jarring caused to knife-edges and planes by putting on and removing 
weights while these were in contact. It must be borne in mind, as a 
golden rule of weighing, that nothing must be added to or removed 
from either pan of the balance when the instrument is in 
motion. In order to shew the movement of the beam, there is a long 



370 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

index finger descending from its centre and moving in front of an ivory 
scale at the bottom of the pillar. A description of the mechanism em- 
ployed to effect these various movements is unnecessary, as they can 
readily be understood by a few minutes careful inspection of the instru- 
ment itself. Some other attachments of the balance will be better 
understood when we come to describe the operation of weighing. If a 
student is working in a laboratory under the direction of a teacher, he 
will find balances there, and already properly adjusted ; in case that he 
happens to have purchased one for his private use, all the adjustments 
will have been made by the maker, and should not be interfered with 
by him, unless he is thoroughly acquainted with the mechanism of a 
balance. It should always be borne in mind that a balance must on 
no account be altered or re-adjusted, except by some responsible person; 
there may be several persons working with the balance, and the one, by 
altering it, and possibly setting it wrong, may upset the work of all the 
others. Suppose a student has procured a balance for his own private 
use, let him place it in its permanent position, which should be on a 
stout bench or table in a dry room, and at a height convenient for 
weighing when sitting down. The light should, if possible, be from a 
window behind the balance ; that is, the balance should be so placed 
that the operator is facing the light, which should not be glaring, while it 
should be good. A light coming from a high window behind the operator 
also answers, but a strong light from either side is not suitable for weigh- 
ing. The first thing to do is to get the pillar of the balance vertical. 
In Wolter's balances there are two spirit levels at right angles to each 
other ; the two levelling screws in front of the balance must be turned 
in one direction or the other until the bubble is in the centre of each of 
the spirit levels ; the balance will then be vertical. In the next place 
carefully dust the beam and the pans with a camel's hair brush. Then 
turn the handle which actuates the balance, and allow the beam to 
vibrate ; it will most likely swing one way or the other immediately the 
beam is liberated, but if not open the right-hand side door and waft a 
very gentle current of air down on the one pan with the hand. Close 
the door again, and watch the vibrations of the index finger ; it should 
be explained that all the sides of the case must be kept closed as much 
as possible during the operation of weighing. The little ivory scale has 
its zero in the centre, the divisions count each way from it, and are 
usually ten in number on each side. Should the balance be correctly 
adjusted the index finger will swing the same number of degrees each 
side of the zero, and after a time, as each vibration becomes shorter, 
will come to rest over the middle of the scale. Strictly speaking, the 
distance travelled on each side must be slightly less than that of the 
other : thus, supposing the index travelled to 9 on the left hand, it 
would, when the balance is correct, swing slightly less than 9 to the 
right, say 8.9 and then back to 8.8 on the left. With a good balance 
this diminution is so little for one or two vibrations that practically we 
may say that it should swing equally on both sides. 

Such a balance as that described costs fifteen guineas, and is capable 
of weighing to the tenth of a milligram, with a weight of two hundred 
grams in the pan. In addition to this instrument a coarser balance is 



ANALYTIC APPARATUS. 371 



also necessary; this should be capable of carrying a kilogram, and 
weighing to the hundredth of a gram. Balances of this kind cost from 
thirty shillings to two pounds, and are similar in principle to that 
already described. 

452. Adjustment Of Balance. — In case when testing the 
balance the index does not swing to the same distance on either side of 
the zero of the scale, first of all again dust the balance most carefully, 
and test once more. In the event of this not removing the error, the 
beam must be re-adjusted; there will be seen two little balls, one on 
either side of the top of the beam, and running on two slender horizontal 
screws attached to the beam — on the side which is the lighter, screw the 
ball very slightly from the centre of the beam, and again test. Repeat 
this until the two sides of the beam exactly counterpoise each other. 
When once adjusted, a balance, if kept clean, needs no alteration for a 
considerable time, providing always that it be carefully and delicately 
handled. In different makes of balance the modes of adjustment vary. 
To describe these in full would go far beyond our present scope ; the 
maker will, however, in every case either give directions or see to the 
proper adjustment of the instrument before it leaves his hands in case 
■of its being a new one. For a very clearly written and most interesting 
chapter on the mechanical principles and management of the balance, 
the student is referred to Thorpe's " Quantitative Analysis," published by 
Longmans & Co. 

453. Analytic Weights. — After the balance, the next thing re- 
quired by the chemical student is an accurate set of weights. As a rule 
the chemist returns his results in percentages, it is therefore of not 
very great importance to him, from that point of view, what unit of 
weight he adopts. In England chemists either use grain weights or 
else those of the French metric system. When grain weights are em- 
ployed, the set contains pieces varying from the hundredth of a grain to 
1000 grains. From its much greater simplicity, weights of the metric- 
system are now used to a much greater extent than grain weights. 
Not only is there this advantage of greater simplicity, but, in addition, 
they are fast becoming the international system for scientific purposes ; 
for this reason, as well, it is highly advisable that all chemists and 
students of chemistry should learn to work with these weights. Those 
who have done so will be unanimous in looking forward with pleasureable 
anticipation to the time when they, or at least some similarly simple 
modification of our own unit of weight, take the place of our present 
complicated system of weights and measures. Whatever weights are 
employed a few very simple factors suffice to convert those of the one 
denomination into those of the other. In chapter I. is given a table of 
the most important metric weights and measures, together with their 
English equivalents. 

The set of weights employed for analytical purposes must be of the 
greatest possible accuracy. They usually range from 50 grams to a 
milligram. The heavier weights are made of brass and then electro- 
gilded ; the fractions of a gram are made of stout platinum foil. In 
.shape, the brass weights are made slightly conical, and are each fitted 



372 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



with a small handle at the top, by which they must be lifted ; for the 
same purpose each of the platinum weights has the top right-hand 
corner bent at right angles to the weight. These weights are arranged 
in a box, each being placed in a separate compartment, those for the 
gram weights being lined with velvet ; the smaller weights are further 
protected by an accurately fitting cover of glass. For the purpose of 
lifting the weights a pair of forceps is provided \ this has its place in 
the box. Analytic weights must on no account be touched 
■with the fingers. Most sets of analytic weights contain the following, 
pieces arranged in the box in the order shown below : — 



50 


20 


10 


10 


5 




1 


1 


1 


2 


0-5 


0-2 


0-1 


0-1 


0-05 


T— I I— 1 I— 1 

o o o 
o © o 

© © o 










0-005 


o-oi 


0-01 


0-02 











Rider. 



The student will require to learn, not only the denomination of each 
weight, but also its place in the box. He must be quite as well able 
to read the weights he has placed in the balance pan from the empty 
spaces as from the weights themselves. As soon as the weights are 
done with they should always be returned to the box ; this should be 
further protected by being kept in a case made for it of wash-leather. 
The accuracy of all analysis depends on that of the weights ; too great 
care cannot, therefore, be taken to preserve them from injury. 

In giving the denominations of the weights above there is a place 
marked " Rider," the nature and use of this particular weight remains 
to be explained. 

The arrangement of the weights, as shown in Figure 75, corresponds 
with the table just given of their value. Special attention must be 
directed to the " Rider," which is drawn to its full size at A. 




FIG. 75- — BOX OF ANALYTIC WEIGHTS. 

The student must now refer again for a moment to the figure of the 
balance previously given ; he will there notice, at the top right-hand 
corner, a milled head, c ; this actuates a rod, at the other end of which, 
from a little hook, depends the rider, as shown just to the left of the 
centre of the beam. From end to end of the beam itself there also runs 



ANALYTIC APPARATUS. 373 



a graduated scale ; this scale is divided into twenty equal parts, the 
centre is marked zero, and the other graduations numbered 1 — 10 from 
the centre towards each end. Each of these units is still further sub- 
divided into 5 or 10 equal parts. This scale is the exact length of the 
beam, measured from one to the other of the terminal knife-edges. An 
inspection of the balance itself shows immediately that, by means of the 
milled head and rod attached thereto, the rider can be placed astride 
the scale at any part of its length. The weight of the rider is one 
centigram, consequently, if placed in the pan of the balance, or at 10, 
the extremity of the scale, the effective weight of the rider is the same 
as its absolute weight. But if it be placed somewhere intermediate 
between the centre and end of the beam its effective weight is between 
and 1 centigram. The effective weight is governed by the well-known 
principle of the lever, namely, that the force exerted by any weight is 
directly proportional to its distance from the fulcrum. As each side of 
the beam is divided into 10 equal parts, the weight of the rider at each 
division is the number of tenths it is from the centre : thus, at 5, its 
weight is equal to -^ of a centigram, or 5 milligrams, and so for each 
graduation and intermediate fraction. The employment of the rider in 
actual weighing will be gathered from the next paragraph. 

454. Operation Of Weighing. — We will suppose that the stu- 
dent has balance and weights in readiness, and requires to obtain the 
weight of some particular piece of apparatus ; this, whatever it is, must 
be thoroughly cleaned and dried, and then placed on the left-hand pan 
of the balance. For this purpose the front of the case of the balance 
may be raised, or if working with one of Wolter's balances, the left- 
hand side door opened. Two rules of weighing are : 1st, always 
place substance in left-hand pan, and weights in the right ; 
2nd, keep the doors of the balance case closed whenever 
possible. Let the weight of the piece of apparatus in question, say a 
crucible, be 17*8954 grams ; we will see how these figures have been 
arrived at. First take the 20 gram weight from the box by means of 
the forceps, and place it in the right-hand pan, release the beam from its 
support by turning the handle : notice whether the left or right-hand 
pan of the balance is the heavier. In this case the weight will be too 
much, and the index finger will swing to the left. Bring the balance 
to rest by turning the handle, and take out the 20 gram weight, and 
replace it by the 10 gram, try whether sufficient — not enough, add 
5 grams — still too little, add 2 — too little, add 1 — too much. Do not 
forget that every time before a weight is added or removed the beam 
must be brought to rest on its supports ; this is always to be done 
gently and carefully. After the addition of each weight the beam will 
have swung over more slowly ; with the 1 8 grams in the pan the swing 
of the index to the left will have been much slower than any preceding 
it, showing that the actual weight of the crucible is being closely 
approached. Return the 1 gram weight to its place in the box, and 
next try 0*5 gram — not enough, add 0-2 — not enough, add 0*1 — not 
enough, add 0*1 — too much. Replace the 0*1 and try 0*05 — not enough, 
add 0-02 — not enough, add 0-01 — not enough, add 0*01 — not enough. 



The weight has now been ascertained within a centigram, because 



374 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

the addition of another centigram would bring the weight up to the 
0*1 gram which has already been tried and found too much. The con- 
clusion of the weighing should now be done with the rider. Place the 
rider on the 5 on the right-hand end of the beam, lower the supports, 
cause the beam to vibrate, and shut the door of the case. If necessary, 
waft with the hand a gentle current of air on to one of the pan in 
order to set the beam in motion. Count the number of graduations 
which the index moves on either side of the zero, it will be found to 
vibrate slightly more to the right than to the left. Next try the rider 
on the 6th division ; this is found too much. Try the rider at inter- 
mediate distances until it is found that the beam swings through an 
equal number of graduations on either side of the zero of the scale ; the 
weight in each pan is then the same. Let us now see how the weights 
are to be read ; this should be done from the box, reading the empty 
spaces. In the case in point these are 10 + 5 + 2 = 17. Against " weight 
of crucible," write this number in the note book. Next read off the 
decigram weights; there are empty, 0*5 + 0*2 + 0*1 = 0*8; write *8 after 
the 17. The centigrams come next, they are 0*05 + 0-02 + 0*01 + 0*01 = 
0*09 ; write 9 after the 8. The milligrams and fractions of a milligram 
are to read off from the rider ; in the present instance the rider stands 
at 0*0054 grams, 54 must therefore be written after the 9. The whole 
figure will then read : 

"Weight of crucible = 17*8954 grams." 
Having thus read the weight from the empty spaces in the box, next 
take the weights out and check the reading off as they are returned to 
their places. This double reading greatly reduces the chances of error 
in recording the weight of the substance. After a little experience in 
weighing, and thus getting to know the capacity of the particular balance 
used, the student should test his balance in order to ascertain the 
value of each graduation of the index scale. To do this put the rider 
on the 5 milligram mark, cause the beam to vibrate, and notice how 
far on either side of the zero it swings. Alter the position of the rider 
until the beam swings from the zero to the 10 on one side * note the 
position of the rider. Suppose it to be on the 5, then 10 divisions of 
the index scale = 5 milligrams, and 1 division = 0*5 milligram. This 
value will only be approximately the same when the pans are loaded, 
but still sufficiently near to save time in the weighing. Thus, suppose 
3*5 grams have been placed in the pan, and the index vibrate 10 to the 
right and 8 to the left, there is no need to successively try the 0*2 and 
other weights down to the 0*01, but the rider may at once be put on 
the 1 milligram mark, and will be found to be very nearly in its right 
place. One or two trials will then find the exact weight. The 1 is 
found in this case by taking half the difference between the vibrations 
on each side ; this will often apply, even though the balance does not 
swing quite to the ten * thus, the distances indicated might be 9 and 7. 
The beam should, however, be always caused to swing freely, as it 
makes a long oscillation in the same time as a short one. It will be 
noticed that, so far, the right-hand side only of the rider scale has been 
referred to ; the left is also frequently convenient. Supposing that, 
with the 3*5 grams above referred to, the index had vibrated the two 



ANALYTIC APPARATUS. 



375 



extra degrees to the left, this would have indicated that the substance 
weighed about 1 milligram less than 3-5 ; to put this weight in would 
require the removal of the 0"5, and the placing of the 0*2, 0*1, 0*1, 0*05, 
0*02, 0*01, O01, on the pan, and the rider at the 9 milligram mark. 
The same result is produced by placing the rider on the 1 milligram 
mark to the left. When the rider is on the left side of the beam the 
weight it represents must be subtracted from that in the right-hand pan. 

The operation of weighing has been described at full length, because 
it is the foundation of all quantitative analysis ; these operations are, 
however, much shorter in practice than they appear on paper. The 
genuine chemical student will never forget that his balance should be 
carefully, intelligently, and even lovingly used. 

In addition to the two balances and set of weights already described, 
the student will need another set of weights, ranging from 10 milligrams 
to 20t) grams. 

455. Apparatus Employed for Measuring purposes. — 

These include measuring flasks, burettes, and other appliances. 




FIG. 76. — VARIOUS MEASURING APPARATUS. 

456. Burettes and Floats.— Figure 76, given above, is an illus- 
tration of various forms of measuring apparatus. The instrument 
marked a is termed a burette, and is used for the purpose of accurately 
measuring small quantities of liquid when delivered. There is at the 
ottom a glass stop-cock ; the tube is graduated throughout. The most 



376 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



useful size of burette is that holding 50 c.c. ; such an instrument is 
graduated in 500 divisions, these are numbered at each c.c, from the 
top downwards. In using the burette it is first cleaned, and then rinsed 
with a little of the solution with which it is to be filled, then filled up 
almost to the top. When a long and narrow tube, such as a burette, 
contains a liquid, the top is not exactly level, but is always slightly 
curved, with, in the case of water and aqueous solutions, the concave 
surface upwards. It is customary, in comparing the height of a liquid 
with the graduation marks, to read from the bottom of this curve, or 
" meniscus," as it is termed. The next thing is to run the liquid out 
through the stop-cock until the zero mark is reached. Fix the burette 
upright in the burette stand, and place the eye level with the zero gra- 
duation, then turn the stop-cock carefully, and let the liquid run out 
until the bottom of the meniscus exactly coincides with the zero line. 
The burette is generally used for the purpose of running a liquid into a 
solution until some particular change takes place, then the height of the 
reagent in the burette is again read off, and the quantity, that has been 
"used, determined. So when the change, whatever it may be, is com- 
plete, again bring the eye level with the bottom of the meniscus, and 
read off the graduation with which it coincides. Accurate reading of 
the burette is much assisted by the use of " Erdmann's Float ; " this 
little piece of apparatus, which is figured below (fig. 77), consists of a 
piece of glass tubing of such a size as to be able to slide readily up and 
down within the burette. The tube is closed at both ends, so as to 
form an elongated glass bulb, which contains a small quantity of mer- 
cury. Around the float a single line, a, is marked with a diamond. 
When using the float it is dropped in the burette and the line around it 




FIG. 77. — ERDMANN'S FLOAT. 



FIG. 78. — MOHR'S BURETTE, 
WITH SPRING CLIP. 



ANALYTIC APPARATUS. 377 



brought to agree with the zero mark at starting, and afterwards the 
.height is read from the line on the float. A form of burette very con- 
venient for general use is that known as Mohr's ; it differs slightly in 
shape from that figured in the preceding illustration. Mohr's burette 
is made either with a glass stop-cock, or else with a glass jet fastened on 
with a piece of india-rubber tubing, as shown in Figure 78. A strong 
spring compresses the tubing, and so stops the burette. The flow of the 
liquid is regulated by means of pressing the two buttons, shown, between 
the finger and thumb. The figure shows only just the lower end of the 
burette. The glass stop-cocks of burettes and other instruments should 
always be slightly greased, so as to prevent their sticking. If a burette 
is likely to be put aside for some time it is well to withdraw the stop- 
cock altogether, and put it away separately. 

457- Pipettes. — Turning once more to Figure 76, there are two 
instruments marked b, b ; these are pipettes, and are used for deliver- 
ing a definite volume of any liquid ; the capacity of the two figured is 
respectively 50 and 100 c.c. In the tube just above the bulb there is a 
mark (not shown in the figure), which indicates the point to which the 
pipette must be filled. When using the instrument, place the lower 
end in the liquid to be measured and suck at the upper until the liquid 
rises above the graduation mark, then stop the upper end with the 
tongue ; next quickly substitute the tip of the finger for the tongue, 
without allowing the liquid to run out. This requires some little prac- 
tice, but repeated trials overcome any difficulty at first experienced. 
Next raise the finger very slightly until the liquid begins to run from 
the lower end ; let it do so until the bottom of the meniscus coincides 
with the graduation mark, then hold the end of the pipette over the 
vessel into which the liquid is to be poured, take away the finger and 
let the tube drain. The pipette, if correctly graduated, will thus deliver 
the exact amount of liquid marked on it. The following are convenient 
sizes for pipettes : 5, 10, 20, 25, 50, and 100 c.c. One 10 c.c. pipette 
will be required graduated throughout its whole length, somewhat like 
a burette ; it is, in fact, used for very much the same purpose. 

458. Measuring Flasks. — The only other piece of apparatus 
that need be explained at present is the graduated flask, d, Figure 76 ; 
this has also a mark round the neck showing the graduation line. The 
same remarks apply to its use as those already made in reference to the 
other pieces of measuring apparatus. 

Other pieces of apparatus required, with the methods of using them, 
"will be described as occasion for their employment arises. 



378 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



CHAPTER XX. 

COMMERCIAL TESTING OF WHEATS AND FLOURS. 

459. Importance of Commercial Testing.— Long experience 

at handling wheats and flours enables the practical miller or baker to 
judge from its appearance the quality of a sample of either wheat or 
flour with, as a rule, considerable accuracy. Still, it is well known 
that such judgments are at times altogether at fault, and that wheats, 
which are apparently similar to the eye, yield flours of very different 
values. In such a country as our own, where enormous quantities of 
wheat and flour are purchased from foreign countries, it is a matter of 
national importance that we get the fullest and best value for our 
money. Hence the author has deemed that the problem of devising a 
simple and trustworthy system of wheat and flour testing is one worthy 
of most serious attention. He ventures to hope that the methods 
suggested in the following pages are at least a step toward the realisa- 
tion of such a system. 

459a. Principles of Commercial Testing.— The first question 

is whether or not those methods usually classed under the heading of 
" analytical " afford information which constitutes any ready guide in 
determining the purchasing value of either wheat or flour. Bearing in 
mind that a commercial assay (or testing) of wheat or flour must be 
simple, capable of speedy performance, and must yield results that shall 
bear directly on the question of value; the author has selected the 
following as the most important analytic determinations to make in 
order to judge the value of wheats and flours : Wheats — weight per 
bushel, weight of 100 grains of average size, strength, stability, colour, 
gluten, and moisture : Flours — the last five of the determinations for 
wheat. In wheats, the weight per bushel and of 100 grains are deter- 
mined on the sample ; for the other determinations a portion of the 
wheat should be ground, and the flour hand-sifted from the offaL 
Strength, stability, and colour should be determined in the dressed 
flour ; gluten and moisture may be determined in either the dressed 
flour or the finely ground whole-meal. The strength, stability, and 
colour are determinations of the physical characters of the flour ; the 
estimations of gluten and moisture are estimations of chemical con- 
stituents of the wheat or flour. The earlier part of this work will have 
made clear the meaning to be attached to each of these determinations ;, 
a description has also been given of the principles involved in their per- 
formance. The whole of these tests are of such a simple nature that - 
their application will be readily understood. 



COMMERCIAL TESTING OF WHEATS AXD FLOURS. 379 

460. Practicability of Commercial Testing.— The fact that 

manures and artificial cattle foods are continually bought and sold by 
analysis, shows that the principle is one which is capable of being 
worked commercially. Custom is undoubtedly the chief obstacle to its 
being successfully adopted in the corn and flour trade. In the open 
market, corn buying and selling is done from sample, and provided the 
bulk of the parcel tallies in appearance and general outward character- 
istics with the sample on which purchase is effected, the miller must 
trust entirely to his own judgment as to quality and yield of flour ; it 
is well known that the opinion formed under these circumstances 
cannot be uniformly depended on. The difficulty is often raised that 
the time during which the purchase of wheat must be effected is not 
sufficient to permit any extended tests being made on the sample. But 
in reply to this objection, even now, arrangements exist by which 
certain allowances are claimed and made on bulk not coming up to 
sample. The London Corn Trade Association conducts a system of 
arbitration by which any such disputes and claims for allowance are 
heard and settled by their making an award. Supposing a system of 
commercial assay of wheat to be adopted for buying and selling pur- 
poses, the corn merchant would offer his samples under guarantee that 
their strength, gluten, &c, were so much, giving the results of assays he 
has had made on his behalf. In case of the buyer finding the bulk of 
the wheat not coming up to the seller's guarantee, he could as now 
refer the matter to arbitration ; the only difference would be that a 
chemist would have a seat on the board of arbitrators, and would certify 
as to the respective merits of the samples in dispute, when subjected to 
a commercial assay. Should there grow up on the part of millers a 
real demand for some more definite system of valuation, as a condition 
of purchasing, than at present exists, the customs of the trade would 
adapt themselves easily enough to the altered circumstances. 

But, after all, is this question of time such a serious obstacle, even as 
matters now stand 1 Provided that a real and steady demand existed 
for such tests, they could, with proper organisation, be made very 
quickly and expeditiously. The author's personal experience of wheat 
and flour testing enables him to state definitely that, provided it was 
guaranteed that a minimum of three hundred samples per year should 
be forwarded to him, he could furnish the results of testing within from 
three to four hours of receiving the samples. In special cases it might 
be possible to complete the testing in two hours. Supposing that such 
samples were forwarded by parcel post, the assays would be commenced 
immediately the samples were received, and the results could be com- 
municated by telegraph. In this way sales could be effected, with the 
results of assays in the buyer's possession, almost, and in many instances 
quite, as quickly as is now clone. At present such results can be 
forwarded very speedily after samples are received ; but in order to 
attain such rapidity as mentioned, a sufficient number of samples would 
have to be received yearly to meet the expenses of the special arrange- 
ments necessary to enable the testing of such samples to be commenced 
on the moment of their arrival. Such tests in the numbers mentioned 
could be made at a fee of a half-guinea each, including the telegraphing 



380 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

of results. With a number of samples sent simultaneously from the 
one firm, and with the ultimate increase in the actual number of samples 
tested yearly, it is probable that this fee could be reduced. Should the 
demand arise, there would be no difficulty in arranging for the making 
of assays in the immediate vicinity of the larger markets : it would then 
be easily possible to take samples at the opening, say, of the Mark 
Lane market, assay them, and return the results before the closing. 
The author has so frequently been asked for particulars as to how a 
scheme of buying by assay would work, that he feels the foregoing 
information will be of interest. 

The buyer of flour is in a somewhat different position to the purchaser 
of wheat : undoubtedly the final test of all flour is the quality of the 
loaf it will make ; so also this is the final test of wheat. The testing of 
wheat by the application of the baking test to the flour produced is 
evidently a method that is not under all circumstances applicable : the 
quantity required, and the time necessary for grinding, and then 
baking, are serious, if not unsurmountable obstacles in the way of the 
miller when purchasing his wheat. The leading bakers are, however, 
at present in the habit of buying their flour after making baking tests 
thereon : in this respect they are more favourably situated than the 
miller. The baking test has the advantage that the whole process is 
familiar to the baker, and is very nearly the exact counterpart of his 
baking operations on the larger scale. He feels that he can trust his 
judgment in the matter of the quality of a loaf of bread, but that he 
could not in the same way depend on the results of any system of 
testing however simple. With the spread of technical education, and 
particularly of a knowledge of the principles of chemistry and analysis, 
the baker will find himself able to form a correct judgment on the 
results also of commercial assays. The information given by such 
assays is of an indirect nature, but it is also frequently wider and fuller 
than that afforded by a single direct baking test. 

While attaching the highest importance to baking tests, the author 
claims that the methods to be described, have the following distinct 
advantages — They can be made on much less flour than is required for 
baking, and also in much less time ; information is afforded, which could 
only be obtained so well, not by one but by a series of baking tests on 
the same flour. Thus, in the strength tests, two or three distinct tests 
are made on the flour with varying quantities of water; these show not 
only the strength but also how the flour bears additional water, over 
and above the quantity required for dough of the requisite stiffness. 
Supposing sixty-eight quarts per sack is the quantity of water required 
for a certain flour, the addition of two quarts more may make the dough 
only slightly slacker ; with another flour, the extra two quarts would 
reduce the consistency of the dough perhaps two or three times as much 
as it did in the first : instances of this are given in chapter XVI., para- 
graph 351. To obtain this information from baking tests, two or more 
should be made with different quantities of water. So too with regard 
to the stability tests, they afford information as to the suitability of 
flours for use in the sponge or dough stage, in what is on the whole a 
more convenient manner than would a single baking test. Another 



COMMERCIAL TESTING OF WHEATS AND FLOURS. 381 

advantage possessed by the system of testing here advocated, is that the 
only variable factor throughout the whole test is the flour being tested : 
no other substance is used which is changeable in its properties ; the 
temperature, &c., are strictly under control; and with small quantities 
and special measuring instruments, both weights and volumes can be 
measured with extreme accuracy. Now to make bread, yeast is re- 
quired, and this substance itself is so susceptible of change that bakers 
of long experience often have difficulty in deciding whether a bad batch 
of bread is due to the yeast or the flour ; again, temperature and other 
working conditions are not so absolutely under control in baking, as in 
the system of commercial testing to be described. 

It must not be supposed that the modes of testing, which form the 
subject matter of this chapter, are intended to supersede and supplant 
the judgment formed by the miller and baker as the result of their 
practicaLexperience ; it is only claimed that they constitute a useful and 
valuable adjunct to that experience, and often give information that is not 
afforded by the ordinary data on which the practical judgment is founded. 

The above remarks have been made on the assumption that such com- 
mercial testings would be made by a professional chemist ; doubtless, 
much of such work would be most profitably performed in that way, 
but with the spread of technical education among a younger generation 
of millers and bakers, they would be perfectly competent to conduct 
such testings for themselves. 

461. Commercial Assay of Wheat. — Directions follow for 

making the various estimations already quoted as constituting a com- 
mercial assay. 

462. Weight per Bushel. — This operation is so familiar to all 
millers that an explanation of it is scarcely necessary. As is well 
known, there is a special piece of apparatus sold that is made for the 
purpose. A cheap and efficient substitute for this may easily be pre- 
pared and used where a student has such a balance as the coarser one 
previously described. Get a coppersmith to make a cylindrical measure 
about 3 inches in diameter and 3 inches deep. Procure from a dealer 
in chemical apparatus a counterpoise box ; these are brass boxes with 
lids which screw on. Put the empty measure on the one side of the 
balance and the counterpoise on the other, fill with shot until it exactly 
balances the measure. Next fill the measure exactly full of distilled 
water, and again weigh, always placing the counterpoise on the weight 
pan. The weight in grams of the water held by the measure represents 
its capacity in c.c. Now the weight of a bushel of water ( = 80 lbs.) 
and that of the water contained in the little vessel are always constant; 
and, as the weight of the water the vessel contains is to the weight of 
the wheat that is being tested, so is the weight in pounds of a bushel of 
water to that in pounds of a bushel of the wheat. Expressing this in 
the usual way we have — 

As weight of water held by vessel : weight of wheat held : : 80 : lbs. per 

bushel j 
or 80 x weight of wheat held weight of wheat in 
weight of water held " pounds per bushel. 



382 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Now for any particular vessel the weight of water it holds is always 

constant, so that 80 in the upper line and the weight of water in the 

lower may be reduced to a single factor, and the weight in pounds per 

bushel at once determined by multiplying the weight of grain, held in 

the measure, by that factor. Suppose that the capacity of the vessel is 

80 
200 c.c, then — — = 0'4 is the factor, and the weight of wheat, in 

200 & [ 

grams, held by the vessel, would simply have to be multiplied by that 
figure. In taking weights per bushel the little measure should be care- 
fully filled and then struck level by means of a pencil or other round 
piece of wood. 

463. Weight Of 100 grains. — For this estimation it is im- 
portant that the grains selected shall represent the average sample: if 
they are simply picked up one by one out of a heap, the weight is almost 
oertain to be in excess of the true average ; for a person under these 
circumstances almost invariably unconsciously selects the largest grains. 
To obviate this, fold a strip of paper, so as to form a V -sna P e cl gutter ; 
take a handful of the wheat and let it pour in a small stream along the 
length of this gutter. Then commence at the one end and count off 
the 100 grains taking each as it comes. Weigh on the pan of the 
balance and enter the weight in the note-book. 

464. Grinding Of Samples. — It is impossible to so grind wheats 
by hand as to produce flours that shall compare with those yielded by 
the same wheats when reduced to flour by the most approved methods. 
But the sample may be ground so as to form flour that shall sufficiently 
well represent the straight grade flour of the wheat, to enable the 
ordinary tests of strength and stability to be applied to the flour. 
Further, though such hand-grinding produces a flour inferior to that 
made in modern milling processes, yet, as all the wheats are before 
testing hand-ground in a similar manner, the results obtained are com- 
parative with each other. 

Mr. Corcoran, of Mark Lane, informs the author that he is now pre- 
pared to supply special small stone mills for the purpose of grinding 
;such samples for testing and analysis. 

Whatever mill is used, first thoroughly clean the interior; then 
weigh the wheat and pass it through the mill ; remove as much as 
possible of the meal from the mill, and weigh it. The stones of the 
mill should be so set as to make as much flour and as little middlings 
as possible. Dress the weighed meal through a sieve covered with 
about No. 9 silk, weigh both the flour and offal. This flour may be 
used for strength and rough comparative colour tests. 

The gluten and moisture determinations may be made either in this 
flour or in fine whole-meal, this latter is best obtained by passing the 
wheat through a drug mill ; that used by the author is a small drug- 
mill, known as the " Enterprise " drug mill. It is of American manu- 
facture, and is efficient and simple. An ordinary coffee mill might 
answer the purpose, but most likely would not cut up the bran 
[Sufficiently fine. The process adopted by the writer is as follows : — 
The mill is set as fine as it will run without clogging. (It need scarcely 



COMMERCIAL TESTING OF WHEATS AND FLOURS. 383 



be mentioned that every part must first be thoroughly cleaned.) The 
wheat is then poured in the hopper and run through as rapidly as 
possible. The grist is next put into a fine sieve, about 20 or 24 meshes 
to the inch, and sifted. The bran is returned to the mill, and run 
through and again sifted ; this operation is repeated on the coarser 
particles until the whole of the meal has been thus sifted. Care must 
again be taken at the end to clean every particle out of the mill and 
add it to the meal ; this is essential, because the latter particles are 
more branny than the former. The meal is next stirred up thoroughly, 
and then stored in a tightly corked or stoppered bottle. The reduction 
of the bran is effected with comparative ease in the drug mill referred 
to, because its action is a cutting one. The simple crushing of such a 
mill as a coffee mill would most likely have but little action on the bran. 
In this way a whole-meal is obtained, which of necessity is an exact 
representative of the grain. It may be asked whether the wheat 
should be cleaned in any way previous to grinding for analysis. The 
answer to such a question is that this must depend on the purpose for 
which the analysis is required. An analysis, made for the purpose of 
buying or selling by, should be performed on a sample representing the 
bulk of the parcel of grain in question ; it should therefore be in no 
way cleaned or washed. When a miller requires to know the analytic 
character of a variety of wheat in the cleaned state, the analysis would 
obviously be made on the sample after cleaning. Undoubtedly the 
safest plan is to analyse the sample exactly as collected, unless the 
analysis is made for some special purpose. If a clean wheat is analysed 
the weight of cleaned wheat obtained from a definite weight of the 
uncleaned wheat should first be ascertained. 

465. Strength. — First, refer back to chapter XVI., and carefully 
read paragraphs 347-351, on strength determinations. The description 
there given may be here supplemented by a few practical directions. 

466. Strength Burette. — Under this heading may be described 
the method of testing flours by the burette only, without any other 
apparatus. In chapter XIX. a description of a burette is given, 
together with an account of Erdmann's float, as a means of reading 
with accuracy the height of the liquid in the burette. The strength 
burette, together with the viscometer, is shown in Figure 80 : at the 
top of the instrument is the zero mark, between which and " 40 " there 
are no graduations ; the tube is then graduated in single quarts down 
to 80 at the lower end. At the bottom a glass jet is attached by means 
of a piece of india-rubber tubing ; this is normally kept closed by the 
spring-clip shown, but may be opened at will by pressing the two 
buttons shown, one on either side. In use, the burette may be held in 
the hand, but is preferably fixed in a burette stand. It may be filled 
either by pouring in water at the top, or by opening the clip and 
sucking it up through the jet. 

Where a number of flours are being tested it is an exceedingly con- 
venient plan to have a water reservoir attached to the burette ; the 
whole apparatus will then appear as shown in Figure 79. 



384 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 




FIG. 79. — BURETTE, ARRANGED WITH RESERVOIR. 

In the lower part of the figure the burette is seen fixed in a stand. 
At a is a second tube opening into the burette above the clip : by 
means of india-rubber tubing, this second tube, «, is attached to a glass 
reservoir, A, which stands on a shelf above the level of the top of the 
burette. By means of a spring-clip at a the liquid in the reservoir is 
shut off from the burette. The burette being empty, open the clip a ; 
the water flows from A upward into the burette ; when the level 
coincides with the zero mark close this clip, and proceed to deliver the 
desired quantity of water by pressing the clip at the bottom of the 
burette. In this manner the instrument may be filled with great con- 
venience and rapidity. 

To test a flour weigh out as exactly as possible one and a-half ounces 
of the sample, and transfer it to a small cup or basin. Next fill the 
burette with water until the level exactly stands at the top graduation 
mark. Then place the cup containing the flour under the burette, and 



COMMERCIAL TESTING OF WHEATS AND FLOURS. 385 

press the clip, allowing the water to run out until down to as many- 
quarts as it is thought likely the flour will require. Then, by means of 
the stirring rod, work the flour and water into a perfectly even dough ; 
try, by moulding it between the fingers, whether it is too stiff or too 
slack : if so, dough up a fresh sample, using either more or less water 
as the case may be. Having thus made a dough of a similar consistency 
to that usually employed, read off from the burette how much water has 
been used. The figures will express without any further calculation 
whatever, how many quarts of water the flour will take to the sack. 
It is well before judging the stiffness of the dough to allow it to stand 
for some time. The author allows his doughs to remain an hour before 
testing them. 

It is not safe to state from the doughing test alone, how many loaves 
a certain flour is capable of yielding per sack ; because different bakers, 
by working in different manners, do not get the same bread yield from 
one and the same flour. Each baker should, therefore, ascertain for 
himself by means of a baking test, working according to his own 
methods, how many loaves he obtains from a sack of any particular 
flour. He can then in the following manner arrange for himself a table 
showing the bread equivalent of the " quarts per sack " readings of the 
burette. To make this test, take a sack of flour and measure the 
quantity of water requisite to make a dough of the proper consistency. 
Then count the number of 2 lb. or 4 lb. loaves it yields on being baked. 
Suppose that the flour takes 70 quarts of water: then dough up a sample 
with the burette, using water to the 70 quart mark and take dough of 
that stiffness as the standard. Any other flour of the same character 
which takes the same quantity of water to make a dough of similar 
consistency will turn out about the same yield of bread. Suppose 
another sample of flour takes 72 quarts of water, then it will make, 
neglecting the slight loss in working, 5 lbs. more dough (one quart of 
water weighs 2 J lbs.) Weighing the bread into the oven at 4 lb. 6 oz. 
per the 4 lb. loaf, every two quarts more water per sack means rather 
over another 4 lb. loaf produced. In exact figures the additional 5 lbs. 
of dough yield 4 lb. 9 oz. of baked bread, or practically 4J lbs. 

In this easy manner, by this instrument, a baker may determine for 
himself, without any but the simplest mental calculation, and working 
according to his own processes, how much bread a particular flour yields. 
It is advised that every baker should for himself construct a table of 
results, based on his own method of working. To do this, let him, as 
suggested, make a trial baking, and find out how many quarts of water 
a sack of any one flour takes, and how many loaves it produces. Enter 
those figures in the table, then for every two quarts more, add on 4 J lbs. 
of bread or 1 J 4 lb. loaves : for every two quarts less substract the 
same amount. 

The following is an example of such a table actually constructed by 
a baker for his own use. A baking test showed that a sack of a par- 
ticular flour took 68 quarts of water and yielded 95 4 lb. loaves. The 
other figures are calculated. Of course, any loss during fermentation 
and general working affects the actual baking test and so is taken fully 
into account. The small percentage of loss on the variations in quantity 



386 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



of dough produced by stronger or weaker flours does not materially 
affect the yield, except in the case of flours which are either very far 
above or below the average. Every baker is strongly recommended to 
make a standard baking test for himself, but the following table agrees 
pretty well with the usual London practice. 



56 quarts per 


sack yield 88 J 


4 1b. 


loaves, 


or 353 lbs. 


of bread. 


58 


89| 




5) 


3571 


55 


60 


901 






J 


362 


55 


62 


91f 






> 


3661 


55 


64 


m 






5 


371 


55 


66 


93J 






5 


375J 


55 


68 


95 






J 


380 


55 


70 


96J 






J 


384J 


55 


72 


97i 






) 


389 


55 


74 


98f 






5 


393J 


55 


76 


991 






J 


398 


55 


78 


lOOf 






) 


4021 


55 



467. Testing With Viscometer. — As already explained, this 
instrument is of value as a means of obtaining an absolute measure of 
the stiffness or viscosity of any particular dough. Any judgment which 
depends on the faculty of touch must of necessity be uncertain ; where 
great accuracy is required, an instrument of this kind gives a mode of 
measurement that is of considerable value. As a preliminary to directions 
for testing with the instrument a description of its various parts is 
given. Figure 80 is an illustration of the viscometer, together with 
a strength burette. 

The figure is a sectional drawing about one-third the actual size of the 
instrument. The lower part, marked a b, is a cylindrical base, through 
which are two lightening holes, marked y z. The cylinder, ef, and 
flange, c d, are cast in one piece ; c d has a collar turned down to fit 
inside a b, the edge of c d is milled. Through the bottom of the 
cylinder is a hole, marked t, the upper edge of this hole is rounded off, 
in order that no cutting edge shall be presented. This aperture may be 
opened or closed at will by the cover, u, which slides between a pair of 
guides, and may be drawn in or out by the rod and milled head, v. 
The piston, m n, consists of a thin disc of steel, the lower edge of which 
is rounded : this piston is attached to the bottom of a trunk, m o, the 
diameter of which is about one-sixteenth of an inch less than that of 
the piston. This piston trunk passes through the cylinder cover, g h : 
in the top of this cover is screwed a tube, ij t carrying at its upper end 
a collar, k I. Both this collar and the cylinder cover, g h, are bored to 
exactly fit the trunk of the piston. The cylinder cover, tube, ij, and 
collar, k I, therefore together act as a guide for the piston, allowing it to 
slide steadily up and down, with the minimum of friction. The bottom of 
the cylinder cover fits over the top of the cylinder, and is secured in its 
place by a pair of studs and bayonet catches, s h. On the upper part 
of the trunk are three lines, p q r, the distance between each pair 
being three-eighths of an inch. This trunk is loaded inside in order to 



COMMERCIAL TESTING OF WHEATS AND FLOURS. 



387 



H 



juarii 



iO^r 




FIG. 80. — VISCOMETER AND STRENGTH BURETTE 

give it the requisite weight. With the exception of the steel piston, 
m n, the instrument is throughout constructed of brass. 

It has been already explained that the sixty-seconds' standard 
adopted for doughs is simply one chosen for convenience. As such 



388 CHEMISTEY OP WHEAT, FLOUR, AND BREAD. 

doughs are slacker than those employed for many purposes, a stifler 
standard may, if wished, be selected ; in such a case the readings may be 
taken, if desired, when the piston has made half its stroke, that is, has 
travelled from r to q instead of the whole distance, r to p. Each 
individual user of the instrument may thus determine on a standard for 
himself. 

Whatever standard is selected, whether the sixty-seconds' standard 
employed by the author, or another, weigh out one and a-half ounces of 
ilour, add water from the strength burette, and dough up the sample as. 
before described, using a quantity of water, which, as well as can be 
judged, shall give a dough of the standard consistency. The dough 
may be mixed by hand in a basin, but the author strongly recommends 
the use of one of Pfleiderer's small doughing machines : these have the 
great advantage that they mix the dough thoroughly, and with absolute 
uniformity. Either place the flour and water direct in the machine, or 
first roughly incorporate them in a basin, and then transfer to the 
machine. The former method is preferable, if one of Pfleiderer's 
absolutely water-tight machines be obtained. Give all doughs the 
same amount of mixing in the machine : this is readily accomplished by 
counting the number of turns given to the driving handle. The author 
drives his from the large pinioned axle, and gives each dough fifty 
revolutions. When sufficiently mixed, take the dough from the 
machine, and set it aside in a small glass tumbler, or other vessel, for 
one hour. Cover over with a glass plate in order to prevent evapora- 
tion. When examining a number of samples, dough them up one after 
the other for an hour, and then come back to the further testing of the 
first one, and take them in rotation. 

Having thoroughly cleaned the cylinder and piston of the viscometer,, 
fill the cylinder with the dough to be tested j to do this slightly open 
the bottom aperture, and push in the dough, through the top, by means of 
a stout brass spatula. In this way fill the cylinder completely, taking 
care that there are no air spaces ; shut the aperture, t, and then, holding 
the cylinder horizontally in the left hand, put on the cylinder cover, the 
piston being at the top of its stroke. Secure it by means of the 
bayonet catches, and stand the cylinder squarely on the base, a b. 
Arrange a vessel, w x, to receive the dough as forced through the 
instrument. Next, have ready a watch with seconds' hand (a chrono- 
graph is the most convenient thing, if one happens to be in possession 
of the worker) ; pull out the milled head, v, the piston begins to 
descend. As soon as the line r coincides with the top of Jc Z, note the 
time, or start the chronograph : note, again, when the line p descends 
to Jc I, and observe how long the piston has taken to travel this distance. 
If exactly sixty seconds, or whatever other standard has been selected, 
the dough is of the standard consistency, and the quantity of water 
used is that required by the particular flour to make a dough of the 
standard stiffness. Eeel the dough with the fingers, and see, especially, 
whether it seems hard or soft. A soft dough, which nevertheless goes 
through the machine slowly, must possess great tenacity. Such flours 
have almost invariably high water-retaining power. The test having 
been made, turn back the bayonet catches, and withdraw the cylinder 



COMMERCIAL TESTING OF WHEATS AND FLOURS. 389 

cover, piston, and guide, from the cylinder. Remove the dough from the 
piston, and clean out the cylinder by means of a spatula. In handling 
the piston be careful not to hold it with the cover end uppermost, as 
the piston rod then slides backwards, and is stopped by the piston 
coming violently in contact with the cover. The piston being very thin 
is liable by rough usage in this way to be forced off the rod. When 
the instrument is done with, the cylinder should be kept soaking in 
water, so as to remove any traces of dough that might clog the valve at 
the bottom. 

Having described the mode of using the instrument, its action on the 
dough may now be examined. In the first place, the lower edge of the 
piston, and the upper one of the aperture through the cylinder bottom 
are both rounded, therefore the dough is not subjected to any cutting 
action. In the next place, the piston during its descent meets with no 
resistance whatever except that due to the dough itself ; as it passes 
down through the hole in the cylinder cover it is impossible for the 
dough to find its way up through that opening against the downward 
movement of the piston ; consequently, there is no clogging whatever 
of the moving parts of the apparatus. The dough, in order to make its 
way out, has to alter its shape so as to pass through the small hole 
at the bottom, consequently its rigidity is here taken into account. At 
the end of the stroke, the piston is found to have pushed out a plug of 
dough from the centre of the cylinder, leaving a ring of dough standing 
round its outside. To force out this plug, the piston must have torn 
away these particles of dough from the annulus (ring) of dough left 
standing. Hence it is that this apparatus registers so thoroughly the 
tenacity of the dough as well as its rigidity. By shading the dough in 
the figure an attempt has been made to indicate the probable lines of 
movement of the dough as the piston passes downwards. An inspection 
of the drawing of the viscometer, and a study of its principles, show 
that it is the condition of the dough, and that only, which can possibly 
affect the speed at which the piston descends. 

Having made one test on a sample of flour, and found whether too much 
or too little water has been added, try next another test with less or more 
water as the case may be, and again examine the dough viscometrically. 
Having obtained a pair of piston readings, one above and the other 
below the sixty seconds (or other pre-determined) standard, the actual 
quantity of water corresponding to the standard may be calculated as 
directed in paragraph 350, chapter XYI. For entering these tests it 
is recommended that a book be procured ruled both ways of the page : 
the strength results should then be entered as shown in Figure 52. 
Supposing 70 quarts to have run through in 90 seconds, and 72 quarts 
in 50 seconds, then on drawing a line connecting these two points, the 
place where it crosses the horizontal line marked 60 in seconds, will 
give the strength in quarts. Thus referring to Flour, No. 11, Figure 
52, the 62 quart dough ran through in 82 seconds, and the 64 quart 
dough in 28 seconds : on these points being joined by a line, it cut the 
60 seconds line at very nearly midway between the 62 and the 64 quart 
line, therefore the strength was taken as being 63 quarts. In this way, 
the strengths of various flours for intermediate points between two 



390 CHEMISTRY OP WHEAT, FLOUR, AND BREAD, 

readings were arrived at. An inspection of Figure 52 shows that the 
upper portions of these lines graphically representing strength are very 
nearly parallel to each other. The author finds if the first test made 
gives a viscometer reading between 45 and 90, that the strength 
may be deduced with sufficient corectness for most purposes in the 
following manner: — On a page, properly ruled both ways, set out two or 
three lines similar to those in Figure 52, representing the strengths of 
different flours. Then, supposing a flour under examination has run 
through the viscometer in 87 seconds, with 68 quarts of water, make a 
mark at that point, and draw from it a line across the 60 seconds line, 
and parallel to the lines of other flours previously set out. Reckon the 
strength from the point where it cuts the 60 seconds line. Such a flour 
would probably have a strength of about 6 9 '5 quarts. Judging from a 
number of flours that have been tested in this manner, the single test 
gives results that very seldom are more than 0*5 quart off from those 
obtained by doughing the flour with two different quantities of water. 

Among other uses to which this mode of testing may be put, the 
author suggests that millers should once or twice a-week examine their 
flours in this manner : they could thus see how nearly they approached 
to constancy in the character of their flour, so far as strength is con- 
cerned. When they were altering their mixture from time to time 
they would be able to trace the effects of the alterations in the mixture 
on the strength of the flour. A continuous record thus kept of the 
actual strength of a flour from week to week could not fail to possess 
great value and interest. 

468. Stability Tests. — As the name implies, these are tests 
made in order to determine the rate at which a softening down of the 
flour occurs during the time it remains in dough. An old-fashioned 
millers' method of testing flours consisted in doughing them, allowing 
them to stand for some twenty-four hours, and then examining the 
stiffness of the dough. Sound flours would stand fairly well, while 
those which were unsound yielded doughs which " ran to water." The 
earlier stability tests, made by the author with the viscometer, were 
simply modifications of these. Samples of doughs were kept 12 or 24 
hours in tumblers with glass covers, which fitted air-tight in order to 
prevent evaporation ; at the end of which time they were tested with 
the viscometer. The results of a number of such tests are given in 
paragraph 351, chapter XVI., and are also represented in Figure 52. 
Some time ago the author had occasion to examine some similar flours, 
and found, to his surprise, that while the earlier samples fell off in 
twenty-four hours some ten or twelve quarts, those clone later fell off 
little or nothing. There was some difficulty in accounting for this, 
until it was remembered that the former flours were tested during a 
hot July, while the latter tests were made in December, during a hard 
frost. This, then, evidently was the explanation : the higher tempera- 
ture caused the gluten to soften and change with far greater rapidity. 
These experiments throw considerable light on one cause why a high 
temperature is so injurious during breadmaking. Apart from any 
action caused by fermentation, dough, composed of flour and water only, 
changes far more quickly in warm weather than in cold. 



COMMERCIAL TESTING OF WHEATS AND FLOURS. 391 

These experiments showed, that in order to obtain constant results in 
stability testing, it was necessary to always work at an uniform tem- 
perature. Comparatively few tests have as yet been made in this direc- 
tion, but the following is the method now adopted by the author in 
determining stabilities. Knowing the strength of the flour, doughs are 
made with respectively 4, 8, and 1 2 quarts less water ; these are placed 
in glass vessels with air-tight covers, and are then kept for six hours in 
a water-bath, maintained at a constant temperature of 25° C. by means 
of an automatic regulator. They are then tested by the viscometer. 
The stability tests quoted in paragraph 425, chapter XVII., were made 
in this manner. 

469. Gluten Testing. — Having in the case of a wheat reduced 
it to a meal, or flour, the gluten estimation may be made. Crude gluten 
has already been defined as the insoluble albuminous matter of wheat 
or flour, together with a small quantity of fat. Its extraction is effected 
by enclosing a lump of dough in fine cloth, and then washing out the 
starch and soluble matters. In order that this operation shall indicate 
the quantity of gluten, it is necessary to conduct it with certain pre- 
cautions to be now described. 

470. The Aleurometer. — Not only should the quantity of gluten 
be determined, but also its character — whether firm and elastic, or soft 
and flabby. For investigating the character of gluten an instrument 
has been devised known as the " aleurometer." The essential part of 
this piece of apparatus consists of a brass cylinder about four inches 
long and one inch diameter ; both the top and bottom can be easily 
removed. Through the top slides a piston rod half the length of the 
cylinder, viz., two inches, and graduated into 25 equal parts, each part 
evidently being the fiftieth of the length of the cylinder. At the bottom 
of this rod is fixed a piston, which is accurately fitted to the cylinder, 
up and down which it readily slides. A weighed quantity of the gluten 
to be tested is placed in the aleurometer, and this in its turn is arranged 
in an oil bath heated by a bunsen flame to a temperature of 150° C. 
(302° F.) Under the influence of the heat the water in the gluten 
volatilises, and causes the gluten to expand, thus raising the piston. 
The degree through which the piston is raised is taken as an indication 
of the quality of the gluten. According to the inventor, a gluten that 
does not raise the piston at all — that is, does not expand to one half the 
length of the cylinder — is unfit for bread making. The instrument, as 
made, has no means for keeping it at an exact temperature, and conse- 
quently its indications are thus rendered untrustworthy. The writer 
has fitted that used in his own laboratory with an automatic tempera- 
ture regulator, such as previously described (chapter XI., paragraph 
279), by which the temperature is prevented from varying ; even then, 
however, the same gluten does not give constant results. The same 
weight from the same flour, in two successive experiments, in the one 
case may not raise the piston at all, and in another forces it to the top. 
The amount of rise depends on the way in which the gluten is manipu- 
lated. The best plan is to roll the required weight, namely, seven 
grams, into a ball, squeezing out as much of the water as possible. 



392 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

After a little practice the results thus obtained agree fairly well, but 
must certainly be not trusted absolutely as a test of strength or weak- 
ness of flour. Some useful ideas may be obtained by inspecting the 
gluten after its removal from the instrument. On tearing open the 
little mass, the gluten from the best flours shows an uniform spongy 
texture, while that which is inferior has either not risen at all or is full 
of big bubbles. The heating for a short time in the aleurometer serves 
another good purpose : the gluten being rendered spongy is afterwards 
dried much more readily than when this treatment is dispensed with. 
The heating for a short time in the aleurometer does not, by decomposing 
the gluten, lessen its weight. Two samples of the same gluten, when 
wet, weighed each 2*25 grams ; one was placed in the aleurometer 
for 15 minutes and then dried in the hot-water oven for 24 hours, this 
then weighed # 922 grams. The second sample was placed in the hot- 
water oven direct, and weighed at the end of 24 hours, when its weight 
was 0*940 grams ; it was again returned to the oven, and after a lapse 
of another 24 hours, weighed 0*917 grams. 

When in gluten determinations it is wished to use the aleurometer, 
30 grams of a flour, or 40 grams of a wheat meal, must be taken. In 
case this instrument is not employed, 10 grams of either flour or meal 
is a sufficient quantity to employ, but even when the aleurometer is not 
used as a measure of the strength of the gluten, it is convenient to em- 
ploy it for the purpose of causing the gluten to expand as a preliminary to 
drying it in the hot-water oven. The method of procedure is, in each case, 
practically the same. The student should commence to practise on flours, 
because of their being simpler to work on than meals. In the following 
directions it is assumed that the aleurometer is to be used, but if not, the 
student can readily make the necessary alterations in his procedure. 

On the pan of the coarser balance weigh out 30 grams of flour, transfer 
to a cup or small basin, and add about 25 c.c. of water by means of a 
pipette. Work into a dough by means of a spatula, allow the dough to 
stand for one hour, and then transfer to the washing cloth. For the 
purpose of washing the sample free from starch, &c, a piece of fine cloth 
is required. Various materials have been proposed for this purpose ; 
muslin and fine calico have been used. The writer finds that fine silk, 
such as is used for dressing flours, answers the purpose admirably ; a 
piece about twelve inches square is required. Wet, and if necessary, 
thoroughly clean the piece of silk. With the spatula take the dough 
from the basin in which it has been mixed, and place it in the centre of 
the silk. By the aid of the spatula thoroughly clean the basin, and 
having got the whole of the dough in the silk, gather the outer edges 
together round it, as though it were to be tied up like a pudding. It is 
necessary to do this carefully, as otherwise there is danger of losing 
some of the gluten during the subsequent operations. Next knead the 
mass between the fingers in a basin of clean water until most of the 
starch seems to have been washed out. Change the water in the basin 
and again go on with the kneading, taking fresh water from time to 
time. The washing should be continued until the water is no longer 
rendered milky. Next squeeze most of the water out of the silk, and 
then open it out. Remove the gluten from the interior, and roll the 



COMMERCIAL TESTING OF WHEATS AND FLOURS. 393 

whole up together ; look carefully over every part of the silk and pick 
•off any little bits and add them to the rest of the mass. The gluten of 
some flours will be found to leave the silk readily and without trouble, 
that of others sticks to it most pertinaciously ; in this latter case the 
reason is sometimes that the washing has not been sufficient. It is well 
to again carefully fold up the silk and wash once more, when often the 
gluten leaves the silk more readily. In case it still remains adherent 
there is nothing for it but to patiently remove every little bit, one at a 
-time. One of the easiest methods of effecting this task is to spread out 
the silk on a piece of glass, and keeping it thoroughly wet, to rub the 
gluten with the wet finger ; the gluten under this treatment becomes 
•detached in little pellets, which must be added to the main lump. The 
.-silk must be gone over in this way until not the slightest bit remains 
on its surface. Another word of caution may be added here : when the 
gluten is soft and flabby, it is with rough treatment sometimes forced 
through the interstices of the silk, great care must therefore be taken 
not to be unduly rough in the kneading. The outside of the silk must 
be looked at in order to see that no such passage of the gluten through 
its meshes is occurring. If, with an unusually soft gluten, such should 
liappen to be the case, the best plan is to wash the silk clean and begin 
again, working with even greater care than usual. 

Having got the whole of the gluten together in a single lump, none 
being left on the silk, another stage in the washing must be commenced. 
Prior to this, place a piece of silk or muslin over the top of a beaker or 
jug, so as to answer as a sieve. Fill a basin with clean water, and 
wash the naked gluten in it. This is best done by dipping the piece in 
and then rubbing it vigorously between the palms of the two hands, 
occasionally giving them a twisting motion. Every now and then 
again dip the gluten in the water. Watch carefully through all this in 
order to see that none is lost. After a little time pour the water 
■away on the piece of silk or muslin arranged as directed, and look to see 
that no pieces remain ; should any do so return them to the main 
piece. Change the water, and go on washing until, even after a 
vigorous rubbing between the palms, the gluten yields no turbidity to 
the water. Great care is requisite for the accurate performance of this 
operation ; the gluten must be watched through every step. It is very 
•easy to err on the one side by not washing out all the gluten, or on the 
other by losing some through careless treatment. 

The mass of gluten from the flour may be here left for a moment, in 
order to point out the method of treating a meal up to this stage of 
gluten extraction. The meal is weighed, made into a dough, transferred 
to the silk, and washed until it no longer causes the water to become 
milky, exactly as before. But now there is a difference : the silk con- 
tains the bran as well as the gluten, and these have to be separated 
-from each other. With the harder wheats this is done without much 
difficulty, but in the case of those that are softer it is sometimes almost 
impossible to recover the whole of the gluten. After having washed 
out the starch, squeeze the water from the silk, and then open it 
out on the piece of glass. There will usually be one fairly sized lump 
of gluten ; take this out and rinse it moderately free from bran in a 



394 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

basin of clean water, next squeeze it well together, then pick off any 
tolerably large pieces of gluten that remain on the silk, and add them 
to the main lump. After each addition, again squeeze the piece together 
and rinse off any loose bran. The difficulty is now to gather together 
any particles remaining in the bran — these are often so small as to be 
scarcely visible. Take the mass of tolerably clean gluten and add to it 
a portion of the bran, roll them together with considerable force between 
the palms, and then wash off the bran. This process of rubbing together 
the main lump of gluten and the bran effects the removal of any little 
fragments of gluten by their sticking to the larger piece ; which, in 
virtue of its adhesive property, picks them out from the bran, just as a 
magnet picks out iron filings from among those of brass. Treat the 
whole of the bran remaining on the silk in this manner ; the result will 
be a lump of gluten still containing a little bran. With a hard wheat, 
however, the whole of the gluten will have been thus recovered ; with 
the softer ones it is sometimes advisable to drain the water off the bran 
and again rub it all up with the gluten. In every case inspect the 
bran most carefully before throwing it away ; the bran should also be 
rubbed between the fingers, this will often detect fragments of gluten 
that escape the eye. Having got the whole of the gluten together, 
wash it time after time until free from bran. This is a tedious opera- 
tion, but one that can be performed by vigorous and careful treatment. 
Pour every lot of water on to the muslin in order to see that no gluten 
is lost. The washing must be continued until the gluten yields no 
turbidity to clean water. 

The gluten, whether from flour or meal, being clean, wipe off any 
adherent water, and weigh on the pan of the coarser balance. From 
30 grams of a flour the weight will probably be from 7 to 9*5 grams. 
Enter the weight in the note book. (At the end of this description 
there will be given an example of how the entering should be made). 
Weigh off exactly 7 grams of the gluten for the aleurometer, and put 
the remainder outside on a wet piece of glass. The fingers and knife 
used for cutting the gluten must be kept moist. After the gluten is- 
weighed, wipe the scale pan quite dry. 

Before arriving at this stage the aleurometer should have been got 
ready for use, by heating it with the help of an automatic regulator to 
a temperature of 150° C. In use, the oil bath of the aleurometer should 
be fixed at a convenient height in the ring of the retort stand, the 
temperature regulator may then also be fastened by means of a small 
clamp to the rod of the stand. The bulb of the regulator must be im- 
mersed in the oil bath, so that its stem passes through one of the holes 
in the top of the inner vessel of the bath. Instead of oil, paraffin may 
be used in the bath ; this is a white, wax-like substance, melting readily 
on applying heat ; it possesses the advantage of not corroding the copper 
so quickly as oil, and also evolves a less disagreeable smell when heated. 
If paraffin be used it must be warmed enough to melt it in the bath r 
and then the inner casing of the aleurometer fitted to its place ; the 
regulator may then also be fixed. Through another hole in the top of 
the casing, a mercury thermometer, graduated to 200° C, should be 
passed in order to test the temperature of the bath. Working at this. 



COMMERCIAL TESTING OP WHEATS AND FLOURS. 395 

temperature the regulator must only contain air ; the adjustment must 
be made exactly as before described. The instrument being finished 
with, always open the air vent before turning off the bunsen. 

Having, by means of the regulator, succeeded in getting the oil bath 
of the aleurometer at a constant temperature of 150° C, the gluten may 
be inserted for the purpose of being tested. Take off the top and 
bottom of the aleurometer, and oil the interior by taking just a little oil 
on the tip of the finger and rubbing over every part of the inner sur- 
face : a small quantity only of oil is necessary for this operation, as 
merely the slighest film is needed. Mould the seven grams of wet 
gluten into a ball, and insert it in the aleurometer, put on both bottom 
and cover, see that the piston slides up and down readily, and then 
place the instrument in its casing in the bath. In about ten minutes 
the gluten will rise ; as soon as it becomes stationary, note the height on 
the scale to which the piston has risen, and enter it in the note-book. 
Before reading the height of piston give it a gentle tap on the top with 
the finger, as sometimes it registers too great a height, owing to the 
formation of a cushion of steam between the upper surface of the gluten 
and the piston. The remaining piece of gluten must now be added. 
Take out the aleurometer and remove the top, drop in the wet gluten, 
again put on the cover, and replace in the bath, let it remain for 
another ten minutes, and then take out. In case the piston has been 
forced to its greatest height, the instrument should be allowed to cool 
somewhat before the top is taken off, as sometimes the pressure of steam 
within is so great as to violently eject some of the gluten, on the top 
being removed. Bearing in mind this caution, take off the top and. 
bottom of the aleurometer and take out the gluten ; if the instrument 
has been properly oiled it is removed with ease. Tear the little roll of 
gluten open, lengthways, and notice its texture ; this should be fine and 
spongy. Also smell the gluten in order to see whether it shows any 
signs of mustiness in its odour. The gluten has now to be dried : place 
it on a dish, labelled with the name or number of the sample, and dry 
it in the hot-water oven for twenty-four hours. At the end of that 
time remove the gluten, allow it to cool in the desiccator for five 
minutes, and then weigh on the analytic balance. These dry rolls of 
gluten are among the very few things which may be weighed direct on 
the pan of the balance. Where time is an object the gluten may be 
weighed earlier, but in ordinary laboratory work it is as well to let the 
glutens remain in the oven over-night. It is a good plan to divide the 
weight of wet by that of the dry gluten, and thus obtain the ratio ; this 
is a useful check against mistakes in weighing. The results should 
appear in the note-book like the following example : — 

Sample of Flour, No. 17. 
Gluten ex 30 grams. 

Wet 8-45 = 28-16 per cent. 

Aleurometer ... ... 47° 

Dry 2-864-9-54 per cent. 

Ratio 2-9 



396 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



Tough and elastic when wet, fine spongy texture after being heated ; 
colour good. 

The calculation of percentages in a case of this kind is very simple. 
As 30 grams have been taken we have : — 

As 30 : 100 : : 8*45 : percentage of wet gluten. 

When the quantity taken is 30 grams the first and second terms of 
the proportion will always be the same, therefore all that is needed is 
to multiply by 10 and divide by 3, an operation readily performed by 
first moving the decimal point one place to the right, and then dividing. 
When 40 grams have been used, employ 4 as the divisor instead of 3 ; 
if 10 be taken, the percentage is at once gained by multiplying by 10. 

471. Hot- Water Oven. — Directions having been given to dry 
the gluten in a hot-water oven, that piece of apparatus must now be 
described. These oveus are usually made of copper, and are of the 
appearance and shape shewn in Figure 81. 




FIG. 8l. — HOT- WATER OVEN. 



The oven consists of an inner and outer casing, with a space between 
them about an inch in thickness ; the top, bottom, two sides, and back, 
are therefore double. This space for about half the height of the oven 
is, when in use, filled with water, which is kept boiling by the bunsen 
flame placed underneath. Anything placed in the oven is thus kept at 
a temperature of from 96 — 100° C, but, while there is any water 
within the casing, never above the latter temperature. In order to 
prevent the oven boiling dry, a little feed apparatus, a, is attached to 
the side ; this, as shown, consists of a copper vessel open at the top, and 
communicating by means of a pipe with the water space of the oven. 
Through the bottom of a is passed a piece of glass tubing, the top of 
which reaches to the height at which it is desired that the water shall 



COMMERCIAL TESTING OF WHEATS AND FLOUES. 397 

remain in the oven. This glass tubing is kept in its place by a piece 
of india-rubber tubing, which, while making a water-tight joint, allows 
the tube to be slidden up or down as wished. Through the pipe at the 
side, marked with an arrow, a small stream of water is led into a ; this 
feeds the oven, and the overflow passes out through the glass tube, 
which should either stand over, or be led into, a drain. The pipe b is- 
arranged so that any condensed steam may also drip into a. 

Another very good plan is to have fitted to the top of the water oven 
an inverted Liebig's condenser ; through the outer casing of which a 
stream of cold water is passed. The steam from the boiling water in 
the casing is then condensed by the condenser, and returned to the 
oven. The oven, having been once filled, will not need replenishing for 
a considerable time, as the loss of water is very little. The condenser 
should be made of brass or copper tubing ; the inner tube about f inch 
in diameter, and the outer 1 \ inch : the length should be from 24 to 30 
inches. The cold water should enter the jacket at the bottom. When a 
condenser is used, the oven should also be fitted with a glass water guage, 
to show the height of the water. With this arrangement the oven may 
be filled with distilled water, and so loss of heat by the formation of 
crust be prevented. 

472. Desiccator. — The desiccator is an instrument composed of 
a glass plate and bell jar, containing within it a small tray filled with 
concentrated sulphuric acid, this keeps the air within dry, and so 
preserves from damp anything placed inside to cool. 

473. Interpretation of Gluten Results. — As the first and 

one of the most important estimations made in the analysis of wheat or 
flour, the method of determining gluten has been described at full 
length. There are several suggested modifications of that that has been 
given, one of the most important being that the sample should be 
allowed to stand a longer time before being kneaded. Whatever method 
is employed, it is of the highest importance that absolute uniformity is. 
observed in the method of testing ; in this way results are obtained that 
may be fairly compared with each other. When giving methods for the 
determination of the soluble albuminoids, reference will again be made 
to the gluten, and a comparison instituted between the results obtained 
by its mechanical extraction, and the total albuminoids, soluble and in- 
soluble, as estimated by purely chemical means. As has been frequently 
said, "It is comparatively easy to estimate the quantity of the gluten, 
but how about the quality ? " The aleurometer is the result of one 
attempt to solve this problem ; it, however, only does so in a somewhat 
rough fashion. With practice in its use, a division of the gluten of 
flours and wheats into strong and weak may be made, but no very fine 
lines of distinction can with certainty be drawn. As a result of experi- 
ence, a judgment can be formed from the feel and appearance of the 
gluten when wet. Some glutens are soft and sticky, possessing at the 
same time but little or no toughness. Others, again, are highly elastic, 
and firm and springy to the touch ; these latter are special qualities 
which render a flour of value for bread making purposes. It will often 
be found that a flour, which yields good baking results, contains only a 



398 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

moderately high quantity of gluten ; the gluten would, however, be 
found on examination to possess those qualities to which favourable 
reference has just been made. 

Generally speaking, a flour which is high in strength but compara- 
tively low in gluten, will absorb a lot of water in doughing; but 
will fall off in fermentation and will lose considerably in weight in 
the oven. A flour of fairly high strength and with gluten high in 
both quantity and quality, will render a good account of all the water 
it absorbs, losing only the minimum quantity either in fermentation or 
in the oven. 

474. Estimation Of Moisture. — Of considerable importance in 
judging the value of a wheat or flour is the estimation of moisture. 
After a little practice with gluten tests, the moisture is a very con- 
venient determination for the student next to make. The percentage 
of water or moisture is usually found by weighing out a definite quantity 
of the flour or meal in a small dish, and then drying in the water oven 
until it no longer loses weight. When a number of samples have to be 
assayed some regular method of procedure is necessary. The following 
method may be adopted : — 

Procure from the apparatus dealer one dozen selected glass dishes, 
2 \ inches diameter. Mark these with the numbers i. to xn. on the 
sides, with a writing diamond. Have a little box made in which to 
keep these dishes. The box should have a shelf, supported a little way 
from the bottom, containing a series of separate holes, one for each dish, 
so that they may be kept without danger of breakage. Clean and dry 
each dish, and then weigh it carefully ; enter the weights in the note- 
book, and, previous to using each dish, test its weight. This may be 
done very quickly, as the weights are already approximately known. 
It will be found that, if used with care, the weight of the dishes will 
remain constant, within some four or five milligrams, for a considerable 
time. Time may be still further economised by having a series of 
counterpoises made for the set of dishes. These consist of little brass 
boxes in the shape of weights, the tops of which can be unscrewed. 
Brass counterpoises of this description can be readily obtained. (Orme 
'& Co., of 65, Barbican, whose name has been already mentioned, have 
made a number of these counterpoises to order of the writer, for use 
with 2J inch dishes. Other special apparatus for wheat and flour 
analyses, devised by the writer, may be obtained from this firm). Have 
engraved on the top of the counterpoises a series of numbers corre- 
sponding to those on the dishes; clean the counterpoises and dishes 
thoroughly, and balance the one against the other in the following 
manner : — Place No. 1 dish in the left hand balance pan, and the corre- 
sponding counterpoise in the other, together with its cover. Fill up the 
counterpoise with shot until it is as nearly as possible of the same 
weight as the dish, then add little shreds of tinfoil until the two exactly 
counterbalance each other ; finally screw the lid and box part of the 
counterpoise together. Proceed in exactly the same way with all the 
dishes. In this case the shelf of the box for the dishes should also have 
little holes cut in it for the counterpoises, so that each may be kept im- 
mediately in front of its particular dish. Having a set of counterpoises, 



COMMERCIAL TESTING OF WHEATS AND FLOURS. 399 



before using each dish test it on the balance against its counterpoise, 
and if necessary adjust the weight with the rider. As the dishes 
gradually become lighter through use, the rider will have to be placed 
on the left-hand or dish side of the balance. In case the balance is one 
which is only fitted with the rider arrangement on the right-hand side, 
the dish may, if wished, be placed on that side, and the weights on the 
left in weighing ; this, however, is liable to lead to confusion and mis- 
takes in reading the weights. As the dishes grow lighter, their weight 
against the counterpoise is really a minus quantity, and should be entered 
as such in the note-book. For a long time the difference between the 
two is inappreciable, but still, for the sake of accuracy, the test should 
always be made. When the dish and counterpoise differ more than 
•005 gram, the latter should be re-adjusted. Having a number of flours 
to do, weigh out exactly 5 grams of each in a dish, then place them in 
the hot-water oven and allow them to dry for 24 hours ; at the end of 
that time the water will be expelled. Take out the dishes, allow them 
to cool in a desiccator, and weigh as quickly as possible. As the weight 
of each is approximately known, put the larger weights on the balance 
pan before taking the dish from the desiccator. After weighing, return 
the dishes to the oven for another hour, and again weigh ; the two 
weighings should agree within a milligram. Dry flour is very hygro- 
scopic ; that is, it absorbs moisture with great rapidity. This is notice- 
able during weighing, for a sample will often gain while in the balance 
as much as five milligrams. The student will at first, for this reason, 
get his weights too high. The best plan is to put on the rider at a 
point judged to be too high, and then at each trial bring it to a lower 
number until it is found to be at one at which the dish is the heavier. 
Then take the lowest figure known to be above the weight of the dish, 
for if the rider now be moved upwards the dish will often be found to 
gain in weight just as rapidly as the rider is moved upward. Before 
the dish is removed from the desiccator for the second weighing, put in 
the pan the lowest weights before found to be too heavy. After a time 
the student will find that he can get his two weighings to always 
practically agree ; he may then, but not till then, dispense with the 
second weighing. It is evident that the flour after being deprived of 
its moisture will weigh less ; the weight taken, therefore, less the weight 
of dried flour, equals the moisture ; this, when 5 grams are employed, 
multiplied by 20 gives the percentage. An example should read thus 
in the note-book : — 

Moisture Determination. 

Sample No. 35, Dish No. vn. 

Weight of dish against counterpoise ... ... — 0*0015 

Flour taken 5 grams. 
Weight after drying 24 hours ... ... ... 4-416 

Weight after another hour ... ... ... 4-415 



Less weight of dish ... ... ... ... — 0-0015 



4-4165 



Moisture = 5 - 4-4165 = 0-5835 
0-5835 x 20 = 11-67 = percentage of moisture. 



400 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



It may be noted in passing that a difference of 5 milligrams in the 
actual weight amounts to just 0*1 per cent, difference in the estimated 
moisture. 

475. Baking Tests. — The following are directions for making a, 
baking test on a comparatively small quantity of flour : the quantity 
used, 3 lbs., produces from 4 lbs. to 4 \ lbs. of bread. This may bo 
baked either in one or two tin loaves. 

First determine strength of the flour, either with the strength burette 
alone, or in conjunction with the viscometer. If the sixty-seconds 
standard is adopted, the dough had better be made with either 4 or 6 
quarts less water, as if water be added to the full viscometric strength, 
the dough is much slacker than that used in many districts. This will 
present no difficulty to the practical baker, who can readily test for 
himself how stiff he requires his doughs to be, and can then either adopt 
his own viscometer standard or make a constant deduction from the 
strength according to the sixty-seconds' standard. 

With 7 lbs. of flour, each ounce of water used is equivalent to one 
quart per sack. For tests on 3 lbs. of flour the water in ounces, equi- 
valent to quarts per sack, is obtained by multiplying by ^ ; thus 50 
quarts per sack equal 21*4 ounces per 3 lbs. of flour. The following 
table gives the proportionate quantity of water for 3 lbs. of flour, from 
50 to 81 quarts per sack : — - 

50 quarts = 21*4 ounces. 



51 


>> 


21-8 


52 


>) 


22-3 


53 


55 


22-7 


54 


55 


23-1 


55 


55 


23-5 


56 


55 


24-0 


57 


55 


24-4 


58 


55 


24-8 


59 


55 


25-3 


60 


55 


25-7 


61 


55 


26-1 


62 


55 


26-6 


63 


55 


27-0 


64 


55 


27-4 


65 


55 


27-8 


Quantities. 


—Flour 3 


yeast | oz 




Weigh all 



66 


quarts 


= 28*3 ounces 


61 


55 


28-7 


68 




)) 


29-1 


69 




5 


29-6 


70 




5 


30-0 


71 




5 


30-4 


72 




5 


30-8 


73 




5 


31-3 


74 




J 


31-7 


75 




) 


32-1 


76 




) 


32-6 


77 




J 


33-0 


78 




} 


33-4 


79 




} 


33-8 


80 




J 


34-3 


81 




) 


34-7 



Weigh all ingredients as accurately as possible. 
First, weigh out the flour, and put it in a pan of sufficient size ; take 
out about an ounce of the flour and put it aside in a small cup. Coun- 
terpoise a jug on the balance, and weigh out the requisite quantity of 
water, warmed to a temperature of about 85° F. Weigh the salt and 
rub it with the hands into the flour; add the weighed yeast to the water 
and mix it thoroughly, taking care to break down any lumps with the 
fingers. Make a hole in the middle of the flour and pour in the yeast 
and water ; stir it sufficiently to work enough of the flour into the water 
to form a thin sponge : cover this over by drawing up a little of the 



COMMERCIAL TESTING OF WHEATS AND FLOURS. 



401 



flour from the sides. Let this stand for an hour in a warm place, 
covered over with flannel. Then knead the whole into a dough. Clean 
all fragments of dough from the hands, and rinse them in a little of the 
reserved flour ; let the rinsings go into the dough. Let the dough 
ferment for from 3 to 4 hours. In the meantime, grease and weigh a 
4 lb. baking tin. Dust a perfectly clean kneading-board with a little 
of the reserved flour, and turn out the dough from the basin, cleaning- 
it as thoroughly as possible with the Angers. Mould the dough into a 
loaf, using up in so doing the remainder of the reserved flour. Transfer 
the loaf to the tin, taking care that as little as possible is lost. Notice 
to what extent the dough has become slacker during fermentation, also 
whether elastic or possessing very little tenacity. Let the dough prove 
in the tin for about an hour, then weigh. Next bake for an hour, or 
an hour and ten minutes, according to the heat of the oven. Remove 
the loaf from the tin and allow it to cool ; in an hour weigh the loaf. 
Note the colour of the crust, odour of the bread when warm, &c. Next,, 
with a sharp knife, cut the loaf across its highest part, note the colour, 
texture, flavour, and degree of moisture of the interior. Keep for a. 
day or two and repeat these observations. 

If it is desired to keep a permanent record of the test, a good plan is 
to place the cut loaf on a sheet of paper, and mark its size round with 
a pencil. A large-sized exercise book, without lines, answers this pur- 
pose very well. The other data may be so arranged as to come inside 
the outline of the loaf. 

If wished, a determination of moisture may be made in the crumb of 
the loaf. 

The above serves as a general method of making baking tests ; the 
time of fermentation, temperature, quantities, <fec, may be varied if 
wished ; but if the object is to compare a series of flours, they should be 
treated as nearly as possible in the same manner. 

The following are given as examples of how baking tests may be 
entered in the note-book : — 

Hungarian Patent. English Wheat Flour. 

77 quarts. 66 quarts. 



Strength 



Flour 
Water 
Salt 
Yeast 



Dough and Tin 
Less Tin 



Dough 

Loss during Fermentation 
Bread 

Loss in Baking 
2 a 



48 ounces. 


48 ounces 


33 


33 


281 


33 


i 




i 






5) 


2 


33 


3 
4 


33 

55 
35 


£ 


h 


82|- 


771 


)> 


... 1031 


99f 




22 


33 
35 


231 
761 


33 


81J 


33 


1 


33 


1 


33 


... 721 


3) 


70J 


» 


9 


33 


H 


3> 



402 CHEMISTKY OP WHEAT, FLOUR, AND BREAD. 

Second dough when moulded and placed in tin was the slacker of the 
two." 

It must be remembered that these baking tests on small quantities of 
fiour are only to be viewed as comparative ; because, as in all operations 
conducted on a commercial scale, the results obtained in practice fall 
below those yielded by direct tests on small amounts of material. Con- 
sequently, it must not be assumed, because 7 lbs. of flour yield a cer- 
tain weight of bread when baked with every precaution taken against 
loss, that the sack of 280 lbs. will yield 40 times that weight of bread. 
Still it is well, from time to time, to gauge the theoretical yield by a 
small test, as information is thus obtained as to how closely the practical 
and theoretical yields agree with each other. By keeping a closer watch 
on this point, many bakers could lessen considerably various sources of 
loss which now occur, and are almost unnoticed. In case it is wished 
to make the baking test a means of estimating how much the actual 
working yield of flours is, a careful comparison must first be made 
between the results obtained by a 7 lb. baking test, and one on a sack 
of the same flour. Divide the yield of bread from the sack by that from 
the 7 lbs : then the quotient may be used as a multiplier in order to 
convert the 7 lb. yield into working yield per sack. Thus, suppose that 
this quotient is 39 : then whatever weight of bread is yielded by a 7 lb. 
baking test, that quantity multiplied by 39 gives the approximate yield 
per sack. But the figures thus obtained must not be relied on too ab- 
solutely, as disturbing elements occur when working on the large scale 
which are avoided when making experimental tests. It is on the whole 
safer to view experimental tests as affording information on the com- 
parative merits of flours, rather than as an indication of absolute yield 
by the flours when baked in large quantities. 



DETERMINATION OF MINERAL MATTERS IN WHEATS AND FLOURS. 403 



CHAPTER XXI. 

DETERMINATION OF MINERAL AND FATTY MATTERS IN WHEATS AND FLOURS. 

476. Determination Of Ash. — To determine ash, weigh a 
platinum crucible or small dish, and then add five grams of the flour 
■or meal ; place the dish on a pipeclay triangle resting on the ring of a 
retort or tripod stand, and burn the flour by gently heating with the 
bunsen. The volatile matter burns off readily, and leaves behind a 
cake of ash mixed with carbon ; the heat must be continued until the 
carbon has disappeared, leaving only the ash, which must be white, or 
of a greyish tint. The heat must not be raised too high ; the burning 
off of the carbon may be facilitated by occasionally stirring it with a 
fine platinum wire. Take care that when this is done none of the ash 
is lost by being removed with the wire. When the burning is complete 
allow the dish to cool in the desiccator, and weigh. 

The normal percentage of ash in flour is about 0*7. The higher 
grades of roller-made flour contain very low percentages of ash. 

477. Determination of Phosphoric Acid, P 2 O s , and 

Potash, K 2 0, in Ash. — When it is desired to estimate both these 
constituents, take 50 grams of flour, and heat in a platinum dish until 
the whole of the volatile matter, and most of the carbon, is burned off, 
then moisten with concentrated hydrochloric acid without removal from 
the dish. Evaporate to complete dryness, first over the water-bath and 
then by gentle ignition with the bunsen. This operation renders the 
;silica present insoluble ; add warm dilute nitric acid to the ash, and 
filter from silica and any unburnt carbon : wash the filtrate with the 
warm acid. The solution thus obtained contains the phosphoric acid, 
together with the iron, lime, and other bases. This solution must now 
be made up to a definite volume in a measuring flask, one half must be 
taken for the phosphoric acid estimation, the other half must be used 
for the determination of potassium. 

478. Phosphoric Acid Estimation.— For the purposes of this 

estimation two special reagents are required, known respectively as 
" Molybdic solution " and " Magnesia mixture." 

479. Molybdic Solution. — Dissolve 150 grams of ammonium 
molybdate, Am 9 Mo0 4 , in a litre of water. Make up a litre of nitric 
acid of about 1*20 specific gravity; this may be obtained sufficiently 
near by taking 500 c.c. of commercially pure acid of 1*4 sp. gr., and 
adding thereto an equal quantity of water. Pour the molybdate solu- 
tion into the nitric acid (the mixture must not be reversed). The 
solution thus obtained must be kept in the dark. 



404 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

480. Magnesia Mixture. — Dissolve 110 grams of magnesium 
chloride, MgCl 2 , and 140 grams of ammonium chloride, AmCl, in 
1300 c.c. of water ; dilute this mixture down to two litres with the 
strongest liquid ammonia. 

481. Mode Of Analysis. — Add to the solution of ash about 100 c.c. 
of molybdic solution, and allow the mixture to stand for at least three 
hours, at a temperature of about 50° C. The top of the hot- water oven 
is a very good place on which to put the beakers during this time ; 
the solution may, if it happens to be convenient, be allowed to stand a 
longer time — all night, for instance — without injury. A bright yellow 
precipitate forms, which contains all the phosphoric acid, together with 
molybdic acid ; but as the composition of the precipitate is not constant 
it cannot be weighed for the purpose of determining phosphoric acid. 
The bases remain in the nitrate. Bring the precipitate on to a small 
filter, and there wash with a solution of ammonium nitrate until the 
washings no longer redden litmus paper. Test the first portion of the 
filtrate by adding a drop of sodium phosphate solution to a very small 
quantity, and warm gently — a yellow precipitate shows that the 
molybdate has been added in excess. Should there be no precipitate, 
some more molybdic solution must be added to the main portion of the 
solution, which must then be allowed to stand as before in a warm 
place. Next dissolve the precipitate in the least possible quantity 
of warm ammonia solution (one part strong ammonia to three parts of 
water). This operation is best performed by pouring the warm 
ammonia on to the filter. When this has passed through, if any more 
of the precipitate remain on the filter, return the filtrate to the filter, 
and repeat this operation until the whole of the precipitate is dissolved. 
While pouring the filtrate back on the filter, place another beaker in 
order to catch any drops of the filtrate. Wash out one of the beakers, 
and also the filter, with the warm ammonia solution. This solution con- 
tains the phosphoric acid as ammonium phosphate ; to it add about 10 c.c. 
of magnesia mixture, and one-third of the total volume of strong am- 
monia, set aside in the cold for three hours, or a longer time if wished. 
Test a small portion of the filtrate for excess of magnesia mixture by 
adding a drop of sodium phosphate solution; in the event of their being- 
no precipitate formed, some more magnesia mixture must be added to 
the solution in order to completely precipitate the phosphoric acid. 
Filter and wash the precipitate with dilute ammonia, dry, and then 
ignite in a weighed platinum crucible, and weigh. Before ignition 
separate the precipitate as thoroughly as possible from the paper ; burn 
the latter separately, and let the ash drop into the cover of the crucible. 
The precipitate, after ignition, consists of magnesium pyrophosphate,. 
Mg 2 P 2 7 . The magnesia mixture precipitates ammonium magnesium 
phosphates, thus : — 

Am 3 P0 4 + MgCl 2 = MgAmP0 4 + 2AmCl 

Ammonium Magnesium Magnesium Ammonium 

phosphate. chloride. ammonium chloride, 

phosphate. 

On ignition the precipitate is decomposed, undergoing the following, 
change : — 



DETERMINATION OF MINERAL MATTERS IN WHEATS AND FLOURS. 405 



2MgAmP0 4 = 



Mg 2 P 2 0, 



+ 2NH 3 + 

Ammonia. 



H 2 0. 

Water. 



Magnesium Magnesium 

ammonium pyrophosphate 

phosphate. 

The reason for completely detaching the precipitate from the filter 
paper is that the carbon of the paper reduces the phosphate to phos- 
phide, thus lessening its weight. 

Magnesium pyrophosphate, Mg.,P 2 7 , contains anhydrous phosphoric 
acid, P 9 5 , combined with two molecules of magnesia, MgO. The 
molecular weight of the salt, compared with that of the acid, is 
Mg 2 P., O r P 2 5 

48 + 62 x 112 = 222. 62 + 80 = 142. 

As 222 by weight of the pyrophosphate contains 142 by weight of 
phosphoric acid, the weight of the precipitate, whatever it may be, must 
be multiplied by i|-i- = 0'64; this gives the phosphoric acid in the 
quantity taken, and when that quantity has been half the total solution 
from 50 grams, the result, on being multiplied by 4, gives the percentage 
of phosphoric acid. 

482. Washing and Ignition of Precipitates. — In all quan- 
titative estimations it must be remembered that none of the substance 
being worked on must be lost ; therefore when transferring a solution 
or precipitate from one vessel to another, rinse out all remaining traces 
of the body. Thus, with the yellow precipitate produced by the molyb- 
date, first carefully pour the supernatant solution down a glass rod, as 
shown in Figure 82, without disturbing the precipitate. 




fig. 82. 

Then fill the beaker with the washing solution and commence filtering. 
In order to remove the precipitate from the beaker, a small brush made 
of a quill is very useful. Cut the stem of a quill across near the 



406 CHEMISTEY OP WHEAT, FLOUR, AND BREAD. 

bottom of the feather end, so as to leave the fibres of the feather pro- 
jecting beyond the stump. Next cut off all the feather except about an 
inch at the bottom ; then with one cut of a sharp scissors or knife cut 
the remaining feather part to a width of about a quarter inch. In this 
way a little brush is made, which readily finds its way round the edge 
of the bottom of the beaker. For washing purposes the chemist uses a, 
" wash-bottle," as shown in figure 83. 




WASH-BOTTLE. 



To make a wash-bottle, fit a good cork (india-rubber is preferable) to 
a 20 or 24 ounce flask. Bore through it two holes, through which pass 
pieces of glass tubing bent, as shown in the figure : the ends of these 
tubes must be rounded off ; to the left-hand one is attached, by means 
of india-rubber tubing, a fine glass jet. The length of the tubes must 
be so arranged that the direction of this jet can be controlled by the 
forefinger of the hand holding the wash-bottle. To obtain a large stream 
of water, pour it from the shorter tube ; on blowing through the shorter 
tube a fine stream of water is projected from the jet on the end of the 
other tube. 

The precipitate is usually dried by placing it together with the funnel 
in the oven. The operation of transferring the precipitate from the 
paper to the crucible requires great care. First thoroughly clean, and 
ignite the crucible and cover ; allow them to cool in the disiccator, and 
weigh. Crucible and cover must always be weighed together. 
While the crucible is cooling get ready a sheet of glazed paper ; this- 
should be black for light-coloured precipiates, and yellow for any black 
precipitates. Trim this paper with either a sharp pair of scissors or 
knife, so as to produce clean cut edges. Also have in readiness a piece 
of platinum wire about a foot in length. Clean the bench and spread 
out the sheet of paper, place on it the crucible and cover. Take the 
filter paper out of the funnel, fold it together at the top and very gently 
rub the sides together so as to detach the precipitate. Hold the paper 
all this while over the glazed sheet ; next open the filter and pour its 
loose contents into the crucible. Having cleaned the paper as thoroughly 
as possible, fold it into a strip about three-quarters of an inch wide ; 
then roll it up into a coil, and wind the platinum wire tightly round it. 
Hold the bunsen burner at an angle of 45 degrees over the crucible 
cover, and burn the paper to an ash in it : the paper will readily leave 
the wire when burned. 



DETERMINATION OF MINERAL MATTERS IN WHEATS AND FLOURS. 407 

In order to ignite crucibles, they are suspended in what are called 
" pipeclay " triangles ; these consist of pieces of common clay pipe, 
threaded on iron wire, the ends of which are twisted together. A 
clean pipeclay triangle is placed on the ring of the retort stand, and 
then the crucible placed on it : the crucible is first gently heated by the 
bunsen, and then more strongly by the foot blowpipe. After ignition 
the crucible is allowed to cool in the desiccator, and then weighed. The 
weight of the precipitate is obtained by deducting from the gross 
weight that of the crucible and the filter ash. 

483. Weight Of Filter Ash. — This determination is usually one 
of the first made by the chemical student. The best filters hitherto 
have been those of Swedish make, but now certain German houses 
supply filters, almost if not quite as good. The most convenient sizes 
for quantitative work are 2 J, 3 J, and 4 \ inches diameter. Several 
packets should be ordered at a time, and it should be stipulated that 
they shall be from the same parcel of paper. To determine the weight 
of the ash, take twenty filters, fold and burn them one or two at a 
time, allowing the ash to drop in a weighed crucible ; ignite until a 
perfectly white ash remains, and again weigh. One-twentieth of the 
weight is taken as that of the ash of a single filter. Provided the 
various sized filters are of the same paper, the ash of one size may be 
calculated from that of another. The areas of circles are as the squares 
of their diameters, consequently the ash of a four-inch paper would 
weigh four times as much as that of a two-inch paper ; other diameters 
could be calculated in the same manner. 

484. Potash Estimation. — To the second portion of the solution 
already prepared, add ammonia and pure ammonium oxalate in slight 
excess ; filter off the precipitated iron and lime compounds. Evaporate 
the filtrate to dryness, and ignite gently in order to expel ammonium 
salts. Dissolve the residue in a small quantity of hot water, filter if 
necessary, add hydrochloric acid in slight excess, and evaporate to dry- 
ness. Dissolve the residue in a very small quantity of water, add some 
platinum chloride solution and a drop of hydrochloric acid, and evaporate 
to a sirupy consistency. If the solution lose its orange tint during 
evaporation, more of the platinum chloride solution must be added. 
Treat the moist residue with strong alcohol, of a strength of at least 
80 per cent., filter off the precipitate on a small counterpoised or weighed 
filter; wash with alcohol until the washings are colourless. Dry at 
100° C. and weigh. The precipitate consists of K 2 PtCl 6 : 487'7 parts 
by weight of this body are equivalent to 94 parts of K 2 (potassium 
oxide). 

485. Counterpoised and Weighed Filters. — When working 

on precipitates that are decomposed by a red heat, it becomes necessary 
to adopt some method other than ignition in a crucible before weighing. 
It is usual under these circumstances to either weigh or counterpoise 
the filter beforehand. If the filter is to be weighed, prepare first of all 
a test-tube shaped stoppered weighing bottle (these can be procured of 
the apparatus dealer). Dry this in the hot-water oven, cool and weigh. 
Fold the filter, insert it in the bottle, and dry in the hot-water oven 



408 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

until the weight is constant. The best plan is to set the filter drying 
over night ; the bottle must, of course, be open while in the oven ; in 
the morning stopper it, allow it to cool in the desiccator and weigh. 
Heturn to the oven for an hour, and then again weigh ; the two weights 
should agree within a milligram ; if not, the drying must be continued 
until they do. The washed hlter and precipitate must first be dried in 
the oven in the ordinary manner, then transferred to the weighing 
bottle, and treated exactly as was the original filter. The weight of 
filter and precipitate, less that of the filter, gives the weight of precipi- 
tate. Where the greatest possible accuracy is required this method 
is to be preferred. 

But when speed is an object, a counterpoised filter may be used. 
Take two Swedish filters, and trim one of the pair until they exactly 
counterpoise each other when tested on the analytic balance. In this 
case they are simply to be weighed direct on the pans. Place the one 
of the papers, folded but unopened, on one side of the funnel, and then 
put in the other, opened in the usual way. Filter and wash, then dry 
both filters, and when weighing, again use the empty paper as a 
counterpoise, placing it on the weight side of the balance. In this 
method of working, the assumption is that the two papers being of the 
same weight to start with, and taken from the same lot of filters, will 
contain the same weight of moisture. Further, that as they are sub- 
jected to the same treatment, they will also counterpoise each other at 
the final weighing. The use of counterpoised filters effects a great saving 
of time, and yields results of sufficient accuracy for most technical 
purposes. 

486. Determination of Fat. — The fat of meal and flour is 
•estimated by treatment with either ether or rectified light petroleum 
spirit (/.<?., benzoline). Either of these reagents, especially if warm, 
dissolves fat with readiness, while none of the other constituents of 
wheat are soluble in these compounds. In order to effect the estima- 
tion, a weighed quantity of the sample is first dried in the hot-water 
•oven, and then treated with repeated quantities of ether or petroleum 
spirit until a small quantity of the reagent leaves no greasy stain on 
being evaporated on a piece of white filter paper. If ether be used, 
that known as " methylated " may be employed. The petroleum spirit 
may be obtained by distilling benzoline, arresting the operation when 
the boiling liquid is at a temperature of 86° C. Both ether and petro- 
leum spirit are extremely volatile and inflammable ; both give off at 
ordinary temperatures an inflammable and explosive vapour. The 
greatest care must therefore be observed in working with tkese substances. 

487. Rectification of Petroleum Spirit. — This distillation 

of benzoline is an operation that should only be performed by a person 
having considerable experience in chemical manipulation, and even then 
is fraught with danger unless every precaution is taken. The distilla- 
tion should be performed in the open air. Take a large glass flask of 
about 120 ounces capacity, fit it with a good cork (indiarubber stoppers 
must not be used) ; bore two holes through the cork, one for the leading 
tube the other for a thermometer. Fit the leading tube by means of a 



DETERMINATION OF FAT IN WHEATS AND FLOURS. 



409 



good cork, to a condensing worm in metal vessel, such as is used for 
distilling water. Fit also by means of a cork the exit end of the tube 
of the condenser to a flask arranged as a receiver ; this cork must have 
another hole bored in it and a two-bulbed thistle funnel, like I in Figure 
84, inserted. Mercury must be poured into this funnel, so as to just 
fill the space between the two bulbs. The distilling flask must be ar- 
ranged on a water-bath, having a tube by which steam may be led into 
it. Having put all the apparatus together, be sure that all the joints 
are tight ; bring water to the condenser by means of tubing, and steam 
to the bath from a vessel within the building. The distillation is thus 
■effected by means of the current of steam, and the steam pipe must 
pass through a small hole made specially for it. The apparatus is thus 
cut off entirely from any naked flames, and the operation can then be 
conducted without danger. Distillation must be stopped as soon as 
the thermometer registers 86° C. Rectified light petroleum spirit, dis- 
tilling entirely below 80° C, and leaving no weighable residue, can be 
purchased from dealers in chemicals for analysis. 

488. Soxhlett's Extraction Apparatus. — As ether and petro- 
leum spirit are so volatile and inflammable, special forms of fat extrac- 
tion apparatus have been devised for this estimation. Their object is 
to keep the liquids out of contact with the air of the room, and also to 
make a small quantity of the reagent suffice by repeatedly doing duty. 
Among the most effective of these apparatus is that devised by Soxhlett, 
and illustrated in Figure 84, in which the complete apparatus is shown 
in section. 




FIG. 84.— SOXHLETT'S EXTRACTION APPARATUS 



410 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Directions will first be given for the fitting up of the apparatus, and 
then its use and the principles involved therein will be described. The 
apparatus proper, known familiarly as a " Soxhlett," is that portion a c; 
this is to be procured from the apparatus dealer. Fit the lower end by 
means of a well fitting cork into a good Bohemian flask, n, preferably 
one with a rounded bottom, and about four or six ounces capacity. To' 
the top of the Soxhlett, «, fit another cork, and through it bore a hole 
for the tube of a small Liebig's condenser, j k. The body of this con- 
denser should be about a foot in length ; the inner tube must have an 
internal diameter of half an inch, and must not be constricted at the 
end — these directions are of considerable importance. Fit a cork and 
bent leading tube to k. Fit up a four ounce flask, 771, with a cork 
through which passes a leading tube and two-bulbed thistle funnel, I. 
Pour sufficient mercury in this funnel to just fill the space between the 
two bulbs. Instead of this flask and funnel, m 7, a small U-tube, about 
§ inch diameter, and with limbs 5 inches long, may be employed. By 
means of a piece of glass tubing bent to shape, this U-tube may be 
corked direct to the top of the condenser, k, and then sufficient mercury 
added to just cover the bend. The whole apparatus is then self-con- 
tained, which is a decided advantage. A small water bath, 0, is also- 
required. 

Dry 10 or 20 grams of the meal or flour for one or two hours in the 
hot-water oven, taking as much as can conveniently be placed in the 
apparatus. Take a square piece of Swedish filter paper, big enough to> 
fold up into a little cylindrical case, i b. Fold this so that no liquid 
can escape through the case except through the pores of the paper, 
even when full. This specially folded filter is easily prepared by taking 
the end of a ruler, or other flat-ended cylinder, placing the end in the 
middle of the paper, then doubling it across the diagonals, and folding 
the corners round the ruler. Transfer the meal to the filter, and drop 
this into the Soxhlett. 

For flours, instead of this folded filter, it is convenient to use a small 
glass percolator : this is easily made by taking a piece of glass tubing of 
such a size as to drop easily into the Soxhlett, and cutting it to about the 
same length as the case, i b. A piece of filter paper is then tied 
securely to the lower end. Ether percolates through flours with 
extreme slowness ; and consequently, when a paper case is used, much 
of the ether simply finds its way through the sides of the case, without 
penetrating the interior of the mass of flour. (Some of the fat deter- 
minations, quoted in the earlier part of this work, are probably low 
from this cause). Attach the Soxhlett to the flask n, and place it on 
the bath. Next see that all lights are extinguished within 10 or 12' 
feet of the apparatus. Bring the ether or petroleum spirit from an 
outer store-room, and pour it in the Soxhlett through a funnel until 
the level of the liquid rises to g ; it will then syphon over into the 
flask n. Next pour in about an ounce more of the liquid, and at once, 
before doing anything else, carry the ether or spirit back to the store- 
room. Next attach the condenser, j k, and push in the corks as tightly 
as possible. Support the apparatus by means of a retort stand, p q r, 
and ring. If using the flask m, place it on a shelf conveniently near,, 



DETERMINATION OF FAT IN WHEATS AND FLOURS. 411 

and connect the leading tube at Jc to that of the flask by means of a 
piece of india-rubber tubing. Connect the lower end of the condenser 
to a water tap by means of india-rubber tubing, and arrange another 
piece to the upper end to take the waste water to the drain. Bring a 
water supply to the bath, and also fix an india-rubber tube leading to 
the drain. Arrange a bunsen underneath the bath. Before going- 
further, once more examine each cork and joint, to see that all are air- 
tight. Turn on a stream of water through the condenser. Next light 
the bunsen, and keep it going with a gentle flame. The ether will soon 
boil ; when it does so, arrange the flame so as to keep it boiling steadily,, 
but not too violently. The ether vapour ascends through d e, and 
drives the air before it up through the condenser, and out of the flask 
m, through the mercury in the funnel Z. As soon as the ether vapour 
reaches the condenser it is condensed, and runs back in a small stream,, 
dropping into the filter i b. The complete condensation is furthered by 
the use of the mercury funnel, which offers a slight resistance, and 
thus prevents the escape of ether while still allowing a passage for air. 
As the condensed ether drops, the body of the Soxhlett fills up to the 
level of g ; the ether then returns to the flask by means of the syphon 
/ g h. It carries back with it the fat it has dissolved out of the meal ' T 
as the ether continues boiling in w, pure ether is continuously distilled 
over, the fat remaining in the flask. By this treatment one quantity 
of ether can be made to act on the same meal an indefinite number of 
times. If all the joints are in good condition, no odour of ether will be 
observed during the whole of the time the apparatus is in work. The- 
apparatus may be allowed to remain in action for an hour or more. 
Turn out the bunsen underneath the bath, and also all other lights in 
the vicinity. Take the apparatus to pieces, cork up the lower flask ;, 
test a drop of the ether remaining in the Soxhlett, in order to see if it- 
contains any fat, by allowing it to fall on a piece of white filter paper, 
when it should produce no stain. 

The ether solution requires next to be evaporated to dryness and the 
fat weighed. 

489. Treatment of Ethereal Solution. — Having obtained an 

ethereal or petroleum spirit solution, containing all the fat in the sample 
being analysed, filter if not perfectly clear. It will be next necessary 
to drive off the solvent, and thus procure the fat in a suitable state for 
weighing. Take, for the purpose of evaporation, one of the counter- 
poised glass dishes, and tare it in the balance, making a note of its- 
weight against the counterpoise. It must here again be mentioned that 
ether vapour is not only inflammable, but also highly explosive when 
mixed with air. In default of special apparatus for the purpose, heat 
the water-bath to boiling, and then take it into a room in which tliera 
are no lights. Partly fill the dish with the ether solution, place it in 
the bath, and allow it to evaporate spontaneously, refill from time to 
time from the flask, and finally rinse the flask with a little pure ether, 
pouring the rinsings into the dish. If necessary, heat some more water 
and replace that in the bath as it becomes cool. When most of the 
solvent, whether ether or petroleum spirit, has been thus driven off, 
place the dish in the oven, heat for two or three hours, and then weigh 



412 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

until constant. Well ventilate the room before any lights are brought 
in. By this method the whole of the ether used is lost ; a special in- 
strument for evaporations of this kind has been devised by Winter 
Blyth, and may be procured from the apparatus dealer. The apparatus 
consists essentially of a circular vessel of cast iron, having a support in 
the centre, on which is placed the dish, and around, a groove into which 
the edge of a bell-jar fits. This groove is partly filled with mercury, 
find so causes the bell-jar to make an air-tight joint with the cast-iron 
vessel. A hole in the top of the bell-jar is provided for a cork. When 
using the apparatus it should be placed on the top of a hot-water bath, 
with the dish containing the ether solution in its place. A leading tube 
is passed through the cork at the top of the bell-jar, and this in its turn 
is attached to a Liebig's condenser, with a receiver arranged for the 
ethereal distillate. The bath requires, under these circumstances, to 
be heated with a small bunsen flame ; a rapid stream of water must, 
however, be sent through the condenser, and the operation should be 
conducted in a good current of air. It is still safer to fit the receiver to 
the condenser with a cork, and also add a mercury thistle funnel to serve 
-as a valve, as in the Soxhlett described in the last paragraph. Where 
practicable it is advisable to reserve a small room for operations with 
-ether, allowing no lights whatever to be used therein, and employing 
steam, generated in a boiler outside the room, for all heating purposes. 
A simpler, and for this purpose, probably as efficient an arrangement 
as Blyth's, is made in the following manner : — Take a piece of glass 
quill tubing, about four or five feet long ; arrange this, by means of 
india-rubber corks, through another piece of glass tubing, about three 
feet in length and an inch diameter, so as to serve as a jacket. Bend 
the two ends of the inner tube downwards, so that the one may be 
attached by a cork to the ether flask, and the other lead into a receiver. 
Fill the jacket with cold water and cork up. Attach the flask, n, con- 
taining the ethereal solution to this condenser, and distil off the ether 
by placing the flask on the hot-water bath, holding it all the time ; in 
two or three minutes the ether will have boiled off, and may be collected 
in the receiver. For these small quantities of ether the jacket will con- 
tain sufficient water to effect the condensation. The concentrated fatty 
solution may next be poured from the flask into the dish, and then the 
flask rinsed out with successive very small quantities of ether. 

490. Another Form of Extraction Apparatus. — The author 

has recently used the form of extraction apparatus shown in figure 85. 
Directions follow for its construction and use. 



DETERMINATION OF FAT IN WHEATS AND FLOURS. 



41a 




A\ 



Of 




d 



a> 



FIG. 85. — SIMPLE FORM OF EXTRACTION APPARATUS. 



Take a large test tube (boiling tube) about 7 inches long and 1^ inches 
diameter, procure a piece of vulcanised india-rubber tubing, of such an 
external diameter that it tightly fits the boiling tube on being pushed 
into it. The walls of this tubing should be an eighth or full eigthth of 
an inch in thickness. Next select a piece of glass tubing, of such a 
diameter that, when placed inside the tube a b, there shall be a space 
all round it of about from y 1 ^ to ^ of an inch. In other words, the ex- 
ternal diameter of this tubing must be from i to T 3 F of an inch less than 






414 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

the internal diameter of the boiling tube. From this tubing, cut a piece 
6 inches long, round off the ends in the blowpipe flame, and slightly 
flange the one end as at c, just as is done with a test tube. Two inches 
irom the flanged end of this tube, with the blowpipe, fuse a hole through 
the side of the tube, from J to \ inch in diameter. These tubes may, 
if wished, be obtained ready made from the apparatus dealer. In the 
next place, a piece of filtered paper must be tied on to the lower end of 
this tube. First of all cut out a piece of very fine muslin or flour 
dressing silk, stretch this over the end, and slip over it a tightly fitting 
india-rubber band, stretch the muslin tight, pulling all creases out 
round the edge. Next put on a piece of thick Swedish or Rhenish 
filter paper, again fixing with an india-rubber band, and very carefully 
smoothing out the creases or tightly folding them down. In the case of 
the paper, this must be done very carefully, so as not to break or tear 
it. Again, over the paper fasten on in the same manner a second piece 
of muslin or silk. The india-rubber bands should all be worked back 
about an inch from the end. Once more, look to see that the whole fit 
neatly and tightly, without any large puckers or creases. Next, as 
•close to the end as possible, bind this tightly round and round with some 
very stong thread ; tie neatly, so as not to allow a big knot to project ; 
and lastly cut the paper and muslin off close to the thread, so as to 
leave no ragged or frayed ends. In this way a sort of drum-head is 
made of filter paper placed between layers of muslin or silk for the 
sake of protection. This constitutes the tube, marked in the figure c d ; 
the filter is shown at d e ; and the hole through the side at /. Next 
■cut off a piece of the india-rubber about f of an inch long. With a 
very sharp pen-knife take a cutting off the interior of this tubing, so as 
to make it about ~q of an inch, or rather less in diameter at the one end, 
while the other is allowed to stand its full thickness ; this then makes 
the cork, g g. To the open end, c, of the tube, c d, fit an india-rubber 
cork, h h ; through this bore a hole large enough to take the end, ij t of 
the inverted condenser tube. This completes the apparatus. In order 
to remove all soluble sulphur from the two corks, g g and h h, soak them 
for twenty-four hours in a beaker, with a good quantity of light petro- 
leum spirit. During this time the beaker should be kept under a 
desiccator, in order to prevent evaporation of the spirit. At the end of 
twenty-four hours take the corks out, wash them in spirit, and give 
them another soaking for the same length of time in a fresh quantity of 
the spirit. They will then have swollen considerably, through absorp- 
tion of petroleum spirit, but in an hour or two will regain their original 
size. 

To perform a fat extraction, weigh out a quantity of the meal or 
flour, sufficient to fill the tube c a up to about the height of the shaded 
part, Z, in the figure. Close the hole / with the finger, and pour in 
the meal by means of a gutter of paper, taking care that none is lost, 
and that none finds its way out through /. Next, by means of the 
cork g g, fasten c d inside the tube a b in the position shown. The 
hole/, must be just below the cork g g. Pour into c d sufficient ether or 
petroleum spirit to saturate the flour or meal, and to form a layer about 
a half -inch deep on its surface. Next, cork in the end of the condenser 



DETERMINATION OF FAT IN WHEATS AND FLOURS. 415 

ij, by means of the cork h h, so that its end is just below the hole/. 
This whole apparatus takes the place of the soxhlett and flask n, shown 
in the previous illustration. The water-bath should be so arranged 
that the end of the tube a b just dips into the water : the condenser 
may be arranged with either the separate flask or small U-tube, just as 
with the soxhlett. Turn on the water through the condenser, and heat 
the bath : by this time the petroleum spirit will have percolated through 
the flour, and collected in the bottom of a b. As soon as the spirit 
boils, its vapour passes through the hole /, in the tube c d, and up the 
•condenser ; the condensed spirit drops on to the top of the flour, through 
which it percolates, taking the fat with it down into the outer tube. 
This operation is allowed to proceed until all the fat is exhausted. At 
times, flours only permit the ether or spirit to percolate with extreme 
slowness : in such cases the apparatus has the advantage that it cannot 
overflow ; for even when the whole of the ether is in c d it leaves a 
considerable space between its upper surface and the hole /. As drop 
after drop finds its way through, it is volatilised and returned to c d, 
leaving its modicum of fat in a b. At the close of the operation, pour 
the fat solution from a b into the counterpoised dish ; rinse out the 
tube with successive small quantities of ether or petroleum spirit into 
the dish. Working with this apparatus, the total quantity of ether 
necessary is so small that no necessity arises for its distillation. 

When one estimation is completed, the exhausted flour or meal must 
be poured out of the inner tube, which should be dusted out with a 
•camel's hair brush ; the next sample may then at once be inserted, 
without any further cleaning or washing of the tube being necessary. 

The apparatus must be taken to pieces as soon as finished with ; 
otherwise the india-rubber corks will swell through absorption of ether 
and burst the tubes. 



416 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



CHAPTER XXII. 

ACIDIMETRY AND ALKALIMETRY. 

491. Explanation Of these Terms. — The measurement of the 
amount of either free acid or free alkali in a solution is often an opera- 
tion of considerable chemical importance. Thus, in flours or meals, the 
acidity is occasionally determined ; the measure of acidity being often 
a useful help in deciding whether or not a sample of flour or wheat is. 
unsound. Flours which contain bran or germ develop acidity much 
more rapidly than those thoroughly purified from the offal. This acidity 
is caused usually by the presence of lactic acid, and is produced, as has- 
been previously stated, by the action of the lactic ferment. This 
organism is always found in greater or less numbers on the bran and 
germ of the grain, and acts by converting the sugar into lactic acid. 
This action is much favoured by damp and warmth. 

492. Normal Solutions: Sodium Carbonate.— The process- 

of acidimetry (acid measuring) belongs to the department of volumetric 
analysis, and hence it becomes necessary to explain some of the terms 
used in that branch of analytic work. There is required a set of 
standard acids and alkalies ; that is, solutions of known and definite 
strengths, and an indicator. The standard solutions are usually made- 
up to normal strength. It is requisite that the exact meaning of this 
term normal should be understood. Normal solutions are prepared so 
that one litre at 16° C. shall contain the hydrogen equivalent of the 
active reagent, weighed in grams. It follows that normal solutions of 
acids and alkalies are all of the same strength, and that equal quanti- 
ties exactly neutralise each other. Decinormal solutions are prepared 
by diluting normal solutions to one-tenth their original strength, and 
are shortly designated as N solutions. The acid and alkali most com- 
monly used are sulphuric acid, H 2 S0 4 , and sodium hydrate (caustic 
soda) NaHO. Both these substances are extremely deliquescent, and 
so cannot be easily weighed with accuracy. It is customary, therefore,, 
to first make up as a starting point a normal solution of sodium car- 
bonate, Na 2 C0 3 . Directions follow for starting from this point and 
making up the necessary solutions. 

Normal sodium carbonate contains 53 grams of the dry salt to the 
litre ; as this solution is seldom employed for any other purpose than 
that of preparing other solutions, a quarter of a litre only need be made. 
Take about 18 to 20 grams of the pure dry salt, heat to dull redness in 
a platinum dish or crucible for about 15 minutes, allow to cool under 
the desiccator, and then weigh out exactly 13*25 grams. Transfer this 



ACIDIMETRY AND ALKALIMETRY. 41 7 

weight to a 250 c.c. flask, and two-thirds fill with water, shake up until 
the whole of the salt is dissolved, and then fill up the flask to the gra- 
duation mark. Keep the solution in a clean dry stoppered bottle. 

493. Indicators : Litmus and Phenolpnthalien.— The next 

step is, with the aid of this solution, to make up a solution of normal 
sulphuric acid. From a study of elementary chemistry, the student 
already knows that it is usual to determine whether or not a substance 
is acid or alkaline by observing its action on litmus. Acids turn a. 
solution of that body red, the blue colour being restored by excess of 
alkali ; when the solution is neutral its colour is violet. Bodies such as 
litmus, which are used in order to determine the completion of any 
particular action, are termed "indicators." To prepare the litmus solu- 
tion, take some litmus grains and boil with distilled water; let the liquid 
stand for some hours, and decant off the clear supernatant solution. Let 
this solution again boil, and add nitric acid drop by drop until it 
assumes a reddish-violet colour, boil for a time, and the colour once 
more becomes blue. Continue this treatment with nitric acid until a 
violet tint is obtained that remains permanent after boiling. The reason 
for this boiling is that the litmus contains some earthy and alkaline 
carbonates ; the carbon dioxide liberated, on addition of an acid gives 
the litmus a reddish tint, and so requires to be expelled by boiling. 
The litmus solution should be kept in an open bottle supplied with a 
small dropping pipette, by which a small quantity can be removed when 
wanted. If this litmus solution be kept in a closed bottle it is apt to 
^become colourless ; the colour may be restored by pouring the solution 
in an evaporating dish, and thus exposing it for a short time to the 
action of the atmosphere. Another indicator, much more delicate than| 
litmus, is phenolpnthalien ; this body, however, possesses the disadvan- 
tage of being unsuitable in the presence of carbon dioxide or ammonia. 
Phenolphthalien is a brownish powder, of which one part is dissolved 
in 30 parts of 90 per cent, alcohol, and one or two drops of the solution 
employed for each estimation. The addition of phenolphthalien to an 
acid solution produces no colour, but with the slightest excess of alkali j 
an intense magenta red is produced. 

494. Normal Sulphuric Acid. — Of normal and decinormal 
acids and alkalies, two litres of each is a convenient quantity to pre- 
pare ; these solutions are best kept in stoppered Winchester quarts, 
which hold just over the two litres. Normal sulphuric acid contains 49 
grams of H 2 S0 4 to the litre. Take about 65 to 70 c.c. of pure sulphuric 
acid of 1'840 specific gravity {i.e., strongest acid of commerce), mix 
this with four or five times its volume of water, allow to cool, and then 
make up to exactly two litres with distilled water. With acid of full 
strength the solution will now be too strong ; it must next be tested 
against the normal sodium carbonate. Fill a 50 c.c. burette with the acid 
solution ; with a pipette pour 20 c.c. of the normal sodium carbonate 
into a porcelain evaporating basin, and add a few drops of litmus. 
Note the height of the acid in the burette, and proceed to add it 
cautiously, little by little, to the carbonate in the dish. Wait between 
each addition until the effervescence is over. Continue adding the acid 

2 B 



418 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

until the solution becomes reddish-violet ; next boil the solution gently 
over a sand-bath for two or three minutes, the liquid resumes its blue 
colour as the dissolved carbon dioxide is expelled. Continue adding 
the sulphuric acid solution, drop by drop at the last, boiling between 
each addition, until finally the colour becomes a permanent violet. 
Read the height of the acid in the burette, deduct the first reading ; 
the difference is the amount of acid required to neutralise the 20 c.c. 
of normal sodium carbonate. Let us suppose that this amount is 
18 - 65 c.c, then as with normal solutions equal quantities should exactly 
neutralise each other, it is evident that the 18*65 c.c. require to be 
made up with distilled water to 20 c.c. ; that is, 20 — 18-65 = 1*35 c.c. 
of water must be added. Measure the total quantity of acid solution 
there is, and add water to it in the above proportion. Suppose that 
there remain 1950 c.c, then as 18-65 : 1950 : : 1'35 to the quantity of 
water that must be added. Add the proper amount of water to the 
solution, shake up thoroughly, and once more test by filling the burette 
and titrating against 20 c.c of the normal sodium carbonate, exactly as 
before described : 20 c.c of the one solution should exactly neutralise 
20 c.c of the other. It should be explained that the term titrating is 
applied to the operation of testing a solution by adding to it a volumetic 
reagent. 

495. Normal Sodium Hydrate. — The next step is to prepare 

a solution of normal sodium hydrate ; this solution contains 40 grams of 
pure NaHO to the litre. Weigh out about 120 grams of pure caustic 
soda of commerce, and dissolve up in a beaker in the smallest possible 
quantity of hot water. Allow the solution to stand for some time, in 
order that any sediment present may subside ; cover the beaker during 
this time with a glass plate. By means of a pipette, draw off as much 
as possible of the clear solution, and dilute it down to two litres. Run 
in this solution from a burette into 20 c.c. of the normal sulphuric acid, 
using phenolphthalien as an indicator. With the quantity directed, 
the solution will be too strong. Calculate the amount of water that 
must be added to bring the solution to its normal strength, and proceed 
exactly as was directed with the normal acid. After dilution, again 
titrate acid against alkali, when 20 c.c of the one must exactly neutra- 
lise 20 c.c. of the other. 

496. Decinormal Solutions. — Having succeeded in preparing 
with accuracy the normal sulphuric acid and sodium hydrate, decinormal 
solutions of these reagents must be made. Measure out by means of a 
100 c.c pipette, 200 c.c of the normal acid, and pour it into the litre 
flask ; fill up to the graduation mark with distilled water, and pour into 
a clean dry " Winchester quart," next add another litre of distilled 
water, and two litres of decinormal acid are prepared. In the same 
manner make up two litres of decinormal soda. Titrate 20 c.c of one 
of these against the other ; these, too, should become exactly neutral, 
when mixed in equal quantities. 

497. Water Free from Carbon Dioxide. — In addition to the 

reagents already described, it is necessary to have, for determinations 
of acidity in flours or meals, some distilled water free from carbon 



ACIDIMETRY AND ALKALIMETRY. 419 

dioxide. This is readily obtained by first rendering some water alkaline 
with caustic soda, and then distilling ; the first portion of the distillate 
.•should be rejected. The caustic soda combines with the carbon dioxide 
that may be dissolved in the water ; and so by this treatment the gas is 
prevented from coming over with the condensed steam. The water 
.should be tested in order to see that no soda has been carried over 
mechanically by too violent boiling. The water must give no coloura- 
tion on the addition of two or three drops of phenolphthalien to 
100 c.c, but should strike a distinct and permanent pink on the 
addition of a drop of -?L soda. 



420 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



CHAPTER XXIII. 

SOLUBLE EXTRACT, ACIDITY, AND ALBUMINOIDS. 

498. Soluble Extract. — The proportion of a meal or flour, soluble 
in cold water, is of importance in judging of the character of a sample. 
This soluble portion is termed the " soluble extract," or " cold aqueous 
extract," and consists of the soluble albuminoids, sugar (maltose), gun) 
(dextrin), soluble starch, and soluble inorganic constituents of the grain,, 
principally potassium phosphate. The solution made for the purpose 
of this estimation is also employed for the determination of the acidity 
and soluble albuminoids. On the addition of even cold water to a. 
flour or meal, chemical action immediately commences, the soluble 
starch being dissolved out of any abraded or ruptured starch granules. 
As a consequence, the soluble extract varies with the time the solution 
is allowed to stand in contact with the flour or meal ; absolute 
uniformity must therefore be adopted in the method employed for 
making this soluble extract. The following is the method employed in 
the writer's laboratory : — Weigh out 25 grams of the flour, and transfer 
to a clean dry flask of from 500 — 700 c.c. capacity, add 250 c.c. of 
distilled water, cork the flask with a clean cork, and shake up vigorously 
for five minutes by the clock. One or two minutes' shaking is sufficient 
to break up any little balls of flour, but in order to ensure perfect 
solution the longer time is recommended. Next let the flask stand for 
25 minutes, making half-an-hour from the time of commencement. In 
the meantime arrange a 10-inch French filter paper, in funnel five 
inches in diameter, both being quite dry, and place a clean dry 
beaker or flask to receive the filtrate. At the end of the half-hour 
most of the insoluble portion of the flour will have subsided ; remove 
the cork, and carefully decant as much as possible of the supernatant 
liquid on to the filter without disturbing the sediment. The filtrate will 
at first be cloudy ; return it to the filter until quite clear, then collect 
for analysis. By working in this way, there being practically none of 
the solid matter of the flour on the filter, any subsequent changes in 
the wet flour do not affect the results. As the speed of filtering varies. 
with different filter papers, it was often found that when both flour and 
water were placed on the filter together that a higher extract was 
yielded by the same flour, simply as a result of a slower filtering paper ; 
there is a further disadvantage, in that when any of the solid matter 
of the flour was allowed to get on the filter it greatly impeded the 
rapidity of filtering. Twenty-five c.c. of this clear filtrate must next be 
evaporated to dryness in order to ascertain the amount of matter it 



SOLUBLE EXTRACT, ACIDITY, AND ALBUMINOIDS. 421 

holds in solution. The glass dishes that were used for the moistures 
are also well adapted for this purpose. Having tared a clean dish 
against its counterpoise, and noted any difference in weight, pour 25 c.c. 
of the nitrate into the dish, and evaporate to dryness over the water- 
bath. 

499. Water-Bath. — This consists of a vessel, usually of copper, 
about 4 inches deep, and of other dimensions, varying with the number 
of dishes for which it is made. In case of a bath specially prepared for 
flour extracts and similar work, one to hold 12 dishes is a convenient 
size; its actual dimensions would then be 12 in. x 15 in. x 4 in. The 
top contains a series of holes about 2 J ins. diameter, one for each dish ; 
to each of these is fitted a cover. A water supply apparatus, similar to 
that used with the hot-water oven, is attached to the side of the bath. 
It is very convenient to have a series of flanged glass rings to drop into 
these holes, on which the dishes are placed ; they are thus prevented 
from coming in actual contact with the metal. These rings are similar 
in shape to the top of a beaker, and are about an inch deep ; in fact, 
the tops of broken beakers are often cut off and utilised for this pur- 
pose. They must be of such a diameter that they just fit in the holes 
of the bath, being supported by their flanges. The reason for their use 
is that the outsides of the dishes are liable to pick up foreign matter 
from the metal of the bath, and so have their weight increased. When 
the dishes are allowed to come in contact with the metal of the bath 
they must be carefully wiped clean before being dried. In use, the hot- 
water bath should have its feed apparatus so regulated as to maintain 
the water in the bath at a depth of about half an inch ; the water must 
be kept boiling at a moderate rate by means of a bunsen burner. The 
evaporation of the fluid in the dishes then proceeds by the action of the 
steam. 

500. Soluble Extract, continued. — On the contents of the 

dish having evaporated to dryness, place it in the hot-water oven for 
24 hours, and then weigh. In order to calculate the percentage of 
soluble extract, it must be remembered that by adding 250 c.c. of water 
to 25 grams of flour a 10 per cent, filtered solution has been prepared. 
It follows that 25 c.c. of the solution contains the soluble extract of 2*5 
grains of flour ; the weight must therefore be multiplied by 40 in order 
to give the percentage. It ought to be mentioned that in strictness 
this is not quite correct, as no allowance is made for the moisture of 
the flour, so that as 25 grams of flour contain about 3 grams of water, 
we really have more nearly 22 grams of flour in 253 c.c. of water. As, 
however, the results are only used for comparative purposes, this is not 
of practical importance. If wished, the soluble extract may be calcu- 
lated out to the exact quantity, when the percentage of moisture has 
been ascertained. A determination of soluble extract should read in 
the note-book — 

" Estimation of soluble extract in No. 29. 

Made up 10 per cent, solution in usual manner, and evaporated 
25 c.c. in dish No. 7. 



422 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Weight of dish against counterpoise ... ... — - 004 

Weight of clish and extract ... ... ... ... 0-139 

Less weight of dish ... ... ... ... —0*004 

Weight of extract .. . 0*143 

0-143x40 = 5*72 per cent." 

Graham suggests that in order to determine roughly the amount of 
soluble extract yielded by a flour that alcohol should be added to the 
aqueous infusion. This would cause the precipitation of the albuminoids,, 
dextrin, and more or less of the maltose. After standing a certain 
time, the amount of precipitate is estimated by its depth. The less 
soluble extract, the less is the quantity of precipitated matter. The 
unfortunate part of this test is that it is difficult to judge accurately of 
the quantity in this way, as at times the precipitate may settle more 
closely than at others. It has been further proposed to filter off this 
precipitate and weigh it. There is, however, no advantage in such a 
course over the method of determining the whole soluble extract, especi- 
ally as the precipitation methods entails an additional filtering. It must 
not be forgotten that this alcohol precipitate is a mixture of several of 
the soluble constituents of the flour, and that it does not consist of 
albuminoids alone. 

501. Acidity of Meals or Flours. — When it is desired to 

make this estimation, the aqueous infusion should be made with the 
water free from carbon dioxide. Pour 100 c.c. of aqueous infusion into' 
a white porcelain dish, add two or three drops of phenolphth alien solu- 
tion, and proceed to titrate with ~ soda. The burette must be read 
before the soda is run out, and then again at the completion of the 
reaction. After the addition of each drop of soda, stir the liquid 
thoroughly ; the reaction is complete when the slightest pink shade 
remains permanent after stirring. It need scarcely be said that the 
dishes and other apparatus must be perfectly clean ; the burette should 
first be rinsed with clean water, and then with a few c.c. of the soda 
solution ; this should be allowed to run away, and then the instrument 
should be filled. Soda solutions tend to cause glass stopcocks to set 
fast, the burette must therefore be washed after use, and before being 
put away the stopcock should be withdrawn and wrapped round with a 
small piece of paper, and again put in its place ; this prevents its- 
sticking. It must of course be seen that it is not so placed as to drop 
out by an accident and get broken. For soda solutions it is preferable,, 
however, to use a burette with an indiarubber tube and spring clip. 
Assuming that the acidity of meal or flour is due to lactic acid (as un- 
doubtedly it is in whole or great part) ; then as 1 c.c of ^j- NaHO is- 
neutralised by 0*009 gram of lactic acid, the No. of c.c used x - 009 
gives the weight of lactic acid in 100 c.c. of the infusion. This quantity 
of infusion contains the acid of 10 grams of the meal or flour, therefore 
No. of c.c. of -N- soda x 0-009 x 10 = percentage of acid in the 
sample — in other words, with the quantities directed the percentage 
equals 0-09 times the No. of c.c. of J* soda used. 



SOLUBLE EXTRACT, ACIDITY, AND ALBUMINOIDS. 423 

502. Estimation of Albuminoids by Combustion Pro- 
cess. — The student is already aware that wheat contains a consider- 
able percentage of organic nitrogenous bodies, and that these have been 
termed albuminoids from their chemical semblance to albumin. Certain 
of these bodies are soluble in water, others are insoluble. Directions 
have already been given for the estimation by mechanical means of the 
insoluble albuminoids, these being classed together for practical pur- 
poses under the one name of gluten. The determination of the soluble 
albuminoids is effected by strictly chemical operations. The most 
elementary of these is that depending on an estimation of the organic 
nitrogen contained in the body. When a nitrogenous organic compound 
is mixed with a large excess of caustic potash or soda, and then heated 
to a dull redness in a vessel out of contact with air, the nitrogen of the 
body combines with a portion of the hydrogen present, and is evolved 
as ammonia ; the carbon comes over in part as carbon dioxide, in part 
as tarry matter consisting of volatile hydro-carbons, and when present 
in large excess may remain in part as free carbon. It is evident that, 
by measuring the quantity of ammonia produced during this operation, 
the percentage of nitrogen in a body may be determined, and thus in- 
directly that of the albuminoids. The evolved ammonia is collected and 
retained by causing the gases produced by decomposition to pass 
through either dilute hydrochloric or sulphuric acid, when it forms either 
ammonium chloride or sulphate. For very accurate analyses it is 
customary to employ hydrochloric acid, and then estimate the ammonium 
chloride in the usual way by precipitation with platinum chloride; for 
technical purposes, however, it is more usual to pass the evolved gases 
through an excess of standard acid, and then determine the amount of 
ammonia by afterwards titrating with standard alkali. In this case 
either normal or decinormal sulphuric acid may be employed. This 
particular analytic operation is usually spoken of as an estimation of 
nitrogen by combustion. 

503. Materials Required.— -A description of the apparatus and 
materials necessary follows. 

504. Soda-Lime. — As caustic soda and potash are very deliques- 
cent, and at the same time disagreeable substances to manipulate, 
" soda-lime " is employed in their stead ; this body is simply lime slaked 
in strong solution of caustic soda, and then evaporated to dryness and 
ignited. Soda-lime may be purchased ready prepared, or may be made 
in the following manner : — Dissolve a pound of crude caustic soda in as 
little hot water as possible, and slake in the solution two pounds of re- 
cently burned quicklime ; add the lime, a little at a time, and stir 
thoroughly with an iron road until all lumps have disappeared. The 
mixture should now be of a thick creamy consistency ; pour into a clean 
cast-iron saucepan or pot, and evaporate to dryness. Raise the sauce- 
pan and its contents to a dull red heat, and then while warm reduce the 
soda-lime to a tolerably fine powder in an iron mortar. Keep in a clean, 
dry, well-stoppered bottle. The powder thus obtained is not deliquescent, 
and keeps for an indefinite length of time. 

505. Asbestos. — Some asbestos is also required ; in the matter of 



» 

424 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

this substance the best is the cheapest (the United Asbestos Company, 
of 161, Queen Victoria Street, supply the best Italian carded fibre at 
three shillings a pound.) 

506. Combustion Furnace. — The combustion is performed in a 
tube, which is heated in a special form of furnace, called a combustion 
furnace. These in their older form were adapted for use, with charcoal 
as a fuel, but those now employed are almost universally designed for 
employment with gas. The actual construction of the furnace may be 
readily gathered from an inspection of the apparatus ; it will therefore 
suffice our present purpose to state that the furnace essentially consists 
of a frame, carrying a row of bunsen burners, by means of which the 
tube is heated ; each individual burner is supplied with a separate 
stopcock, by which it may be turned on or off independently of the 
others. The part of the furnace designed for the reception of the com- 
bustion tube is enclosed with small fire-clay tiles, by means of which the 
heat is retained ; these tiles are moveable at pleasure. Kerslake, of 
Bristol, has recently introduced a very cheap and simple form of com- 
bustion furnace. It has the additional advantage of being economical 
in the matter of gas consumed. 

507. Iron Combustion Tubes — For making combustion tubes 
a difficultly fusible variety of glass tubing is commonly used, but when a 
number of analyses have to be made, iron combustion tubes are far more 
convenient, and are now frequently employed. Get an intelligent gas- 
iitter to make them as represented in Figure 86. He should select some of 
the tubing known as wrought-iron barrel, about seven-eighths of an 
inch external diameter, and cut off a piece rather over 20 inches long, 
one end is then to be welded up as shown, a b ; for b c a piece of tubing 
nine inches long and a quarter-inch bore is required. In order to 
connect the two a hole must be bored at b and tapped ; a thread is 
then to be cut on the smaller tube, and the one screwed into the other 
as tight as possible. A good joint, made in this way, should be perfectly 
air-tight after being heated to redness. The open ends at a and c must 
be carefully filed out, so as to present a smooth surface to corks. Be- 
fore use each tube must be made redhot in the furnace throughout its 
whole length — branch as well as the main portion. 

508. U-Tube. — The acid used for the purpose of collecting the 
evolved ammonia is most conveniently placed in a " U-tube " with three 
bulbs, d ef; the limbs of this tube should be eight inches in length. 
Fit a good cork to a, and pass through it a leading tube of glass, which 
is connected by means of a second cork to the U-tube ; the further end 
of the U-tube should also be fitted with a cork and small piece of bent 
glass tubing, as shown ; also cork up c with a good cork. All these 
joints must be made with great care, as it is essential that none of them 
shall show the least signs of leakage. This constitutes the apparatus 
necessary for the combustion. 

509. Description of the Analysis. — The first step in making 

the analysis is to evaporate down a portion of the solution, the prepara- 
tion of which has already been described, to dryness. Take a porcelain 
evaporating basin about five inches in diameter, and pour into it 50 c.c. 



SOLUBLE EXTRACT, ACIDITY, AND ALBUMINOIDS. 



425 



cu 



mm 



•i\AAWVVWWWVY*A/vy 



&¥ 



WM. 




4, 



FIG. 86. — COMBUSTION AND U-TUBES. 

of^the solution. Next add about an ounce of recently ignited fine sand ; 
this should be spread in as thin a layer as possible over the bottom. 
Evaporate over the water bath ; it is well to stop just short of dryness, 
as the perfectly dry residue is only got out of the dish with difficulty. 
In case the residue has become quite dry and brittle, it again softens 
on being kept a few hours. Having cleaned the combustion tube and 
U-tube, and got all the apparatus required in readiness, heat over a 
bunsen burner in an iron dish sufficient soda-lime to about half fill the 
combustion tube ; let this cool, and pour about half of it on the residue 
in the evaporating basin. By means of a thin steel spatula detach the 
residue from the basin and carefully mix with the soda-lime. Break 
down any lumps with a pestle, and when the whole is thoroughly mixed 
transfer to the combustion tube. This may be effected by putting the 
mixture on a piece of glazed paper and then pouring it down the combus- 
tion tube, the smaller end of which must be corked. Having cleaned 
out as much as possible of the residue from the dish, pour in two or 
three drops (not more) of water and just a pinch of soda-lime, give the 
dish a careful rinsing with the mixture, which dissolves off any residue 
still adhering to the dish. Mix this with some more of the soda-lime 
and transfer to the tube ; finally rinse out the dish with the remainder 
of the soda-lime, and pour it into the tube. The soda-lime and residue 
will now rather more than half fill the tube. Holding the branch piece 
upright, tap the tube gently on the bench in order to make a passage 
along the top of the soda-lime mixture for the escape of the evolved 



In order to prevent any particles of soda-lime being mechanically 
carried over by the gases liberated during the act of combustion, a plug 
of asbestos is inserted in the open end of the tube. Take a sufficient 
quantity of this material to form a plug about two inches in length, and 
heat it in a crucible over a bunsen flame for about a minute in order to 
drive off any traces of ammonia. Then insert the asbestos far enough 
in the tube to allow about an inch clear between it and the cork. This 



426 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

plug must fit sufficiently tight to retain any solid matter, while it must 
also allow sufficient passage for the gas. In order to test the plug, un- 
cork the small end of the combustion tube and suck at it a moment in- 
order to learn whether air passes freely through the tube ; then recork 
this end. The tube must next be placed in the combustion furnace- 
with the open end a (figure 86) projecting from the furnace about three- 
inches. Next pour 25 c.c. of decinormal soda in the U-tube, previously 
cleaning it, and attach to the combustion tube as shown in the figure. 
Take care that all the corks fit tightly without leakage. If necessary,, 
support the U-tube by pieces of blocking. The apparatus is now ready 
for the commencement of the combustion ; but before lighting any 
burners have a final look to see that everything is quite right ; in par- 
ticular, notice that the small end of the tube at c is tightly corked. 
Place the tiles of the furnace by which the tube is enclosed in their 
proper place, and turn on the main gas supply, next open the stop-cocks 
of the burners under that portion of the combustion tube which is not 
filled with soda-lime ; let these burners remain on until the fore part of 
the tube is at a dull red heat. Should the outer end of the tube become 
so hot as to char the cork, pour a little water on it and turn out one or' 
two of the end burners of the furnace. It is a good plan to wrap a. 
little tow around the end of the tube outside the furnace and cause- 
water to drop on it from a can with a tap at the bottom, suitably placed. 
A very little water allowed to drop in this way continuously will be- 
sufficient to prevent any over-heating of the cork. During the time- 
that the outer part of the tube is being heated the air should escape in 
bubbles through the acid in the U-tube : should it not do so there must 
be a leak ; the most frequent reason is that the small end of the com- 
bustion tube is at times left uncorked. As soon as the outer part of 
the tube attains a dull red heat, turn on the burners under the mixture,, 
two at a time, at intervals of two or three minutes. The rate at which 
these burners should be turned on depends on the rapidity with which 
gas is being evolved through the U-tube. The gas should escape in a 
gentle stream of bubbles with a distinct interval between each ; should 
the gas escape very slowly more burners may be opened ; in case the* 
gas comes off too quickly turn one or two burners out. Very little 
practice will enable the student to so regulate his heat as to get the gas- 
coming off at the proper rate. The aim is to make the combustion as 
rapidly as is consistent with the thorough absorption and retention of 
he whole of the ammonia by the acid in the U-tube. When the whole 
of the tube is at a full red heat, the combustion may be considered 
complete ; at this stage the bubbling of the gas through the U-tube will 
also have ceased. Toward the end of the operation, discontinue the- 
flow of water on the tow around the end of the tube in order that the 
cork may get sufficiently hot to drive over any moisture which may 
have condensed thereon. The combustion being over, turn off the gas 
from the furnace; as the tube cools, the liquid in the U-tube will recede 
toward the furnace ; uncork the small end at c and draw a gentle cur- 
rent of air through the tube by an aspirator attached to the exit-tub& 
at d. The air can be drawn through by sucking with the mouth, but 
as the gases contained within the tube have an unpleasant taste and 



SOLUBLE EXTRACT, ACIDITY, AND ALBUMINOIDS. 427 

odour, this method is seldom employed, especially as an aspirator is so 
easily constructed. Take a flask of twenty-four or thirty-two ounces 
capacity, fit to it a cork ; through which bore two holes for glass tubing. 
Pass one piece of tubing down to the bottom of the flask and bend it 
over at right angles just outside the cork. The other piece of tubing- 
should be about a foot long and must be just passed through the cork, 
so that all its length projects out of the flask. To use this aspirator, 
fill the flask with water, replace the cork and connect the end of the 
tube which reaches to the bottom of the flask by means of indiarubber 
tubing to the exit-tube, //. Pinch this tube between the finger and 
thumb and invert the flask over the drain. The water tends to run 
out through the long tube, and does so on the removal of the pressure 
on the rubber tube ; at the same time it draws the air after it through 
the combustion tube. Air to the extent of three or four times the 
volume of the combustion tube should thus be drawn through in a gentle 
stream. The object of this is to sweep out any traces of ammonia the 
tube may contain and cause their absorption by the acid in the U-tube. 
When sufficient air has passed, turn over the flask and disconnect the 
indiarubber tubing. Carefully withdraw the cork from a, and by means 
of the wash-bottle, blow a small stream of water into the glass tube in 
order to wash its contents, if any, into the U-tube. It may be of in- 
terest to mention that of late the writer has used a bent tube connecting 
a with/ of drawn brass instead of glass ; it has the advantage of being 
unbreakable, but requires careful cleaning. 

The acid in the U-tube requires next to be titrated with decinormal 
soda. Pour the acid out into a porcelain evaporating basin, and rinse 
the U-tube thoroughly with distilled water, adding the rinsings to the 
main portion of the acid. Add two or three drops of litmus solution, 
and then run in the soda from the burette until the neutral point is 
reached. As the acid is usually somewhat coloured by the products of 
the combustion, it is sometimes rather difficult to determine with ex- 
actitude when the reaction is complete, as the litmus remains of a violet 
shade even after the addition of several drops of the soda. The colour 
can frequently be seen better in a thin layer of the solution, therefore 
pour most of the acid in a clean beaker and note the tint of the small 
quantity remaining in the basin, if too red add a little more soda, and 
pour back the acid solution from the beaker, stir up, and again pour off 
the most of the solution. By operating in this manner the point of 
neutrality can be determined with accuracy. This will have completed 
the analysis ; it now remains to calculate the results. As 25 c.c. of JL 
acid were taken, it follows that that quantity, less the volume of ^ soda 
required to neutralise the acid after the combustion, has been neutra- 
lised by the evolved ammonia. The easiest way to continue the ex- 
planation will be to give the results of an analysis, which will also serve 
the purpose of showing how such results should be entered in the 
note-book : — 

" Estimation of soluble albuminoids in No. 30 by soda-lime combustion. 

50 c.c. of 10 per cent, solution evaporated to dryness with sand. 

Combustion performed as usual. 



428 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

25 c.c. of _N sulphuric acid in U-tube. 

21-45 
4-30 



** soda required == 17*15 

Acid neutralised by evolved ammonia = 

25— 17-15 = 7-85 c.c. 

7-85 x0*177 = l*39 per cent, of soluble albuminoids." 

The entry quoted will be plain, except the multiplying by 0*177 in 
order to obtain the percentage of soluble albuminoids ; the student now 
requires to see the reason for this step. Decinormal sulphuric acid con- 
tains 0*0049 grams of H 2 S0 4 to the c.c. ; ™ ammonia, by which J^. acid 
would be exactly neutralised, contains 0'0017 grams of NH 3 , or 0*0014 
grams of N per c.c. Every c.c. of ^ acid neutralised by the evolved 
ammonia represents, therefore, 0*0014 grams of nitrogen evolved from 
the contents of the tube ; consequently the number of such c.c. multi- 
plied by 0*0014 gives the weight of nitrogen yielded by the substance 
being analysed. Albuminoids contain g-.^-y of their weight of nitrogen, 
therefore the weight of nitrogen evolved multiplied by 6*33 gives the 
weight of albuminoids. It next remains to calculate from this the per- 
centage. When 50 c.c. of a 10 per cent, solution have been taken, that 
quantity contains the soluble matter of 5 grams of the meal or flour, so 
that the percentage is obtained by multiplying by 20. The whole of 
this calculation is shown below : — 

7*85 x (0*0014 x 6*33 x 20) = 1*39 per cent. As the figures within the 
brackets are constant (i.e., never vary in different analyses) they may be 
multiplied together once for all, and the result used' as a constant factor 
or multiplier : — 

0*0014 x 6*33 x 20 = 0*177 = factor. 

In this way the figure given above has been obtained. The student 
must remember that this factor is only applicable when the quantities 
directed have been used. 

The iron tubes after each combustion should have the asbestos taken 
out and reserved for further use ; they may then be cleaned by filling 
them with water, and allowing them to stand for a time ; then, by 
means of an iron or steel rod, loosen the mass of soda-lime and wash it 
out. 

510. Estimation of Albuminoids by the Ammonia 

Process. — In addition to the soda-lime or combustion process for the 
determination of albuminoids, there is another method of estimating 
these bodies known as the " Ammonia Process." Wanklyn and Chap- 
man invented this process, and first applied it to the determination of 
nitrogenous organic bodies in potable waters. It was soon found that 
it was also applicable to the estimation of the albuminoids in such 
substances as wheat, flour, and similar bodies. In Wanklyn and Cooper's 
little work on bread analysis the authors describe the process, and even 
claim for it superiority, from the point of view of accuracy, over the 
soda-lime combustion method already explained. It is doubtful, 



SOLUBLE EXTRACT, ACIDITY, AND ALBUMINOIDS. 429 

however, whether this opinion would be endorsed by the majority of 
chemists ; nevertheless the process, from its being so much more quickly 
performed, can often be advantageously substituted for the more 
tedious combustion method. With sufficient care, and the observing of 
certain precautions, results can be obtained that agree most closely with 
those yielded by nitrogen combustions. The student should practise the 
two methods against each other ; he will then, in all probability, find 
that for most purposes the ammonia process is sufficiently accurate. 

511. Principle of Ammonia Process. — The method depends 

on the fact that most nitrogenous organic bodies, on being boiled with 
a solution of caustic potash (KHO) and potassium permanganate 
(K 2 Mn 2 8 ), evolve a portion of their nitrogen as ammonia. If the 
steam be condensed in a Liebig's condenser, the quantity of ammonia 
may be determined in the distillate {i.e., the distilled water which 
comes over). The actual quantity of ammonia in the distillate is. 
extremely small, recourse is therefore had to " Nessler's Ammonia 
Test ; " this test depends on the fact that " Nessler's solution," the 
composition of which is given below, produces a brown colouration in a 
water containing the merest trace of ammonia. The actual quantity of 
ammonia is judged by the depth of tint produced, compared with that 
caused by a solution of ammonia, or an ammonium salt of known strength. 
As the quantities of ammonia that have to be measured are small, and 
as ammonia is always present in both ordinary water and air, it becomes 
necessary to use special precautions to prevent error. The reagents 
necessary will be first described, then the apparatus used, and lastly, 
the method of making the analysis. There will be required Nessler 
solution, distilled water free from ammonia, standard solution of 
ammonium chloride, and alkaline permanganate solution/ 

512. Nessler's Solution — Dissolve 62*5 grams of potassium 
iodine (KI) in about 250 c.c. of distilled water; set aside a few c.c. of 
this solution. Prepare a cold saturated solution of mercury chloride 
(HgCl 2 ) by adding the finely powdered salt to water, and shaking up so 
long as any is dissolved, then adding a little more, and warming gently 
until this also is dissolved. Then cool the solution ; the excess of 
mercury chloride will separate as crystals, and the solution is known to 
be saturated. Should no crystals be thus formed on cooling the solu- 
tion, it is probable that not sufficient of the salt has been added, add 
therefore a little more, dissolve by gently heating, and again cool the 
solution. Having thus prepared a saturated solution of mercury 
chloride, add this to the potassium iodide solution until the precipitated 
mercury iodide ceases to be re-dissolved on stirring. When a permanent 
precipitate is thus produced, add the small portion of potassium iodide 
solution which was set aside, so as to dissolve this precipitate. Then 
continue adding the mercury chloride solution until a very slight per- 
manent precipitate is obtained. (The object of setting aside a small 
portion of the potassium iodide is to enable the mixture to be made 
rapidly, without danger of over-shooting the quantity of mercury 
chloride necessary.) In the next place dissolve 150 grams of solid 
potassium hydrate, fused stick or cake, in 150 c.c. of distilled water; 



430 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

cool the solution, and add it gradually to that previously prepared. 
Make up the whole with distilled water to one litre. This solution 
throws down a slight brown precipitate ; allow it to stand until it 
becomes clear, and then decant it, without disturbing the sediment, 
into a clean bottle. The solution will now be of a pale greenish-yellow 
colour, and is ready for use. As strongly alkaline solutions have a 
tendency to set glass stoppers, it is a good plan to store this reagent in 
a, bottle having an india-rubber stopper. A smaller bottle should be 
tilled from the store bottle, and kept for use. 

513. Distilled Water Free from Ammonia.— A still and 

condenser should be reserved specially for the preparation of this reagent. 
A four to six gallon still of copper is most convenient. Thoroughly 
rinse both the still and condenser, then fill the still with water, 
and render it distinctly alkaline by the addition of sodium carbonate. 
Commence to distil, and collect the water in Winchester quarts. The 
iirst bottle or two are almost certain to contain ammonia, they must 
therefore be rejected for this purpose, but may be used for ordinary 
analysis. After one or two bottles have been thus distilled, proceed to 
test the distillate for ammonia. To do this a " Nessler glass " is re- 
quired : these are little cylindrical jars of colourless glass about six 
inches high, and holding about 170 — 180 c.c. ; they should have a 
graduation mark on the side of 50 c.c, and a second at 100 c.c. (These 
may be ordered from the apparatus dealers as " graduated Nessler 
glasses.") Wash a Nessler glass and place it under the condenser, and 
thus collect in it about 100 c.c. of the distilled water. Place the glass 
on a clean white porcelain tile, and add to the water, by means of a 
small pipette, 1 c.c. of Nessler solution ; stir the two together by taking 
the glass in the hand and giving it a rotary motion. Cover the top of 
the glass with a watch glass, and allow it to stand for five minutes. If 
the water be free from ammonia it will remain perfectly colourless on 
looking down through it on to the tile, but if any be present the water 
will have assumed a yellow tint. Should it be thus shown to be impure, 
the distillation must be proceeded with and the water again tested after 
a,bout another half a Winchester has come over. As soon as the water 
is thus found to be pure, proceed to collect in Winchesters which have 
been most carefully cleaned and finally rinsed with some of the pure 
water itself. Fill each bottle to the neck, stopper tightly, and tie down 
with paper. Continue to distil until the still contains only about half 
a gallon. Using a clean still and having fairly pure water at disposal 
to start on, five or six Winchester quarts of pure water may be obtained 
from four gallons placed in the still. 

514. Standard Solution of Ammonium Chloride. — Dis- 
solve 1-5735 grams of pure ammonium chloride (NH 4 C1) in a litre of 
distilled water free from ammonia, of this take 200 c.c, and make up 
to two litres with ammonia-free water. This latter solution will con- 
tain ammonium chloride corresponding exactly to 0*00005 grams of 
ammonia (NH ;j ) per c.c. Store the solution in a stoppered Winchester, 
and fill a small bottle from it as required for use. Keep the store bottle 
carefully tied down with paper. 



SOLUBLE EXTRACT, ACIDITY, AND ALBUMINOIDS. 431 

515. Alkaline Permanganate Solution. — Dissolve in a large 

glass flask 400 grams of fused potassium hydrate and 16 grams of potas- 
sium permanganate in 2500 c.c. of ordinary distilled water. Set the 
flask over a sand bath and boil rapidly until the volume is reduced to 
two litres. Let it cool and store in a stoppered Winchester. 

The operation of boiling a liquid in a large glass flask is fraught with 
•considerable risk of cracking the flask. The boiling may instead be 
•conducted in a perfectly clean cast-iron saucepan or pot • in this case, 
however, a portion of the permanganate is decomposed by the iron; this, 
liowever, may be remedied by using an excess of the permanganate. 

516. Apparatus Required in Ammonia Process.— Having 

.given directions how to prepare the special reagents required in this 
^estimation, it is now necessary to describe the apparatus required. The 
solution of the meal requires to be boiled in a retort or flask with the 
alkaline permanganate solution, and the steam condensed and collected. 
For the boiling, a glass flask may be employed ; but when boiled in glass 
:such solutions are apt to " bump " violently, and a number of retorts 
are likely to be broken unless great care is taken. In case a glass re- 
tort is used, carefully bend the stem of a 24 or 30-ounce retort in about 
its middle, so that when the retort is fixed in the retort stand the first 
portion of the stem may be ascending, and that part which is connected 
to the condenser inclined downwards. In this way any portions of the 
liquid that may be mechanically carried over with the steam, on im- 
pinging on the sides of the retort stem, flow back into the retort. 
Bohemian flasks with rounded bottoms seem, on the whole, to stand the 
violent bumping better than retorts. The writer strongly recommends 
the use of a flask of sheet copper, which may be obtained to order from 
the apparatus dealer. The flask should be three inches in diameter and 
:six inches high to the place where the side is tapered off to the neck ; 
the neck must be three-quarters of seven-eighths of an inch diameter, 
and must be slightly flanged outwards at the top, in order to take a 
cork. The joints must all be brazed. Such a flask would have a 
capacity of about 700 c.c, and is shown in Figure 88, which represents 
the whole apparatus as fixed for working. Select an indiarubber cork, 
having one hole, that tightly fits the flask. Take a piece of glass 
tubing three-eighths of an inch external diameter, bend this to an angle 
of about 80°, so as to form a leading tube, as shown in the figure ; 
slightly draw out in the blow-pipe flame the one end, so that it easily 
enters the glass tube of the condenser. Round off the ends of this tube, 
and pass the one through the indiarubber cork. 

The condenser is an ordinary Liebig's condenser, about 18 inches long 
in body, and needs no further remark. 

Select two graduated Nessler glasses, in which the actual distance 
from the bottom of the jar to the 100 c.c. mark is the same. Measure 
this distance, and divide it into 20 equal parts on a piece of paper or 
thin card. Use this as a scale, and thus graduate each jar. The marks 
should be cut on the side of the jars with a writing diamond. The jars 
will thus be graduated at intervals of 5 c.c. ; draw the 10 c.c. marks a 
little longer than those intermediate. Orme & Co. supply Nessler jars 
.graduated at every 5 c.c. 



432 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

Procure a globular pipette, ungraduated, but of about 100 c.c. 
capacity, and with the lower part of the tube sufficiently long to reach 
to the bottom of a Nessler glass when bent, as shown in Figure 87 ; 
bend this tube as there indicated. Cut the tube above the body of the 
pipette to about a length of one inch, and round of the edge. Prom an 
indiarubber dealer procure a pear-shaped indiarubber ball, such as is 
used for an injection syringe, and attach it to the top of the pipette. 




FIG. 87. — NESSLERISING PIPETTE. 

517. Method of Making the Analysis.^-In making these 

estimations it is convenient to make several at a time rather than one 
only. The same solution as that made up for the soluble extracts serves 
for these analyses ; a beginner will find four solutions sufficient for him y 
but after a time he may make up six. The object is to get a sufficient 
number for a day's work, and no more than can be done during day- 
light, as the solutions must not stand over night. A little judgment is 
required in order to so arrange the several operations so as to avoid loss 
of time ; this is, however, soon obtained by experience. The following 
will probably be the best way to arrange the work : — 

Supposing that four wheats or flours are to be analysed, commence 
work early in the morning by taking 125 c.c. of alkaline permanganate 
solution, putting them into a large flask or retort, and adding thereto 
about a litre of tap water. Put this on a tripod and boil briskly, apply- 
ing the flame direct to the bottom of the retort, until the volume is 
reduced to 750 c.c. Toward the end of this boiling operation attach the 
flask or retort to the Liebig's condenser, collect 50 c.c. of the distillate 
in a Nessler glass, and test as before described for ammonia. If the 
tap water is good, the distillate should be free from ammonia, if traces 
are still present, add 250 c.c. of ammonia free water, and continue dis- 
tilling and again test. In case the original solution does not give off 
the whole of its ammonia in being reduced from 1125 to 750 c.c. a larger 
quantity of tap water must be taken to commence with; this will speedily 
be learned by experiment. This operation being complete, there remains 
in the retort 750 c.c. of dilute alkaline permanganate, containing 25 c.c. 
of the concentrated solution to 150 c.c, and free from ammonia. Pour 



SOLUBLE EXTRACT, ACIDITY, AND ALBUMINOIDS. 433 

this solution into a clean flask, rinsed immediately before use with tap 
water, and cork it up. This boiling is best conducted in a large brazed 
copper flask. Before boiling, the flask with its contents should be 
weighed ; then as 375 c.c. have to be evaporated, the boiling must be 
continued until the flask and contents shall have lost, in weight, 375 
grams. 

The reason for this boiling operation is that all water, unless specially 
purified, contains ammonia ; further, except the greatest care is taken,, 
ammonia-free water again absorbs ammonia from the atmosphere,, 
therefore, as a large quantity is required, it is more convenient, and 
also safer, to thus prepare it immediately before use. This treatment 
also expels any traces of ammonia that may have remained in the 
alkaline permanganate solution. When good drinking water is obtain- 
able the quantity of ammonia it contains is usually evolved considerably 
before the volume is actually reduced to 750 c.c. It is a good plan tc 
first collect each 50 c.c, and test it separately, noting how much has to 
be distilled over before the last trace is expelled. Should this point be 
reached much before the volume is reduced to 750 c.c. the liquid may 
afterwards be boiled down to the required volume, and the testing 
dispensed with. It should even then, however, be occasionally repeated,, 
and must never be omitted whenever a fresh lot of the alkaline per- 
manganate solution is made up. Having set this solution to boil, 
proceed to make up the 10 per cent, flour or meal solutions as has been 
directed. Label all the flasks, funnels, beakers, (fee, used, with a 
numbered label, so that no confusion may arise. 

While the solutions are filtering, proceed to fit up the flask and 
condenser. In the case of the new flask, boil it out most thoroughly 
with some caustic potash and permanganate, rinse it well with tap 
water, and set aside completely filled with water. Whenever the flask 
is finished with, for the time being, it should always be filled with 
water and put away corked. The indiarubber cork and leading tube, 
when new, should be soaked for a time in dilute soda solution, and 
then washed thoroughly. Supposing that the flask and leading tube 
are not being used for the first time, pour away the water which was 
put aside in them, rinse them out with tap water, about a quarter fill 
the flask with water, insert the cork, and set the flask to boil. Mean- 
while send a stream of water through the tube of the condenser, and 
then connect it up in the usual way with the water tap, so that the 
stream of the condensing water enters the jacket at the lower end, 
arrange a second piece of tubing to convey the overflow water to the 
drain. Having scalded out the flask and leading tube, disconnect them, 
pour out the water, and put 150 c.c. of the ammonia-free dilute alkaline 
permanganate solution in the flask, replace the cork, and connect up to 
the condenser, as shown in Figure 38. In order to make a tight joint 
between the leading tube and the condenser, cut a piece of red vul- 
canised rubber tubing about an inch long, slide this over the end of the 
leading tube, and then insert it into the condenser tube, so that the outside 
of the rubber tubing just fits into the condenser. Wash a Nessler 
glass and place it under the far end of the condenser tube, so as to 
receive the distillate. The general arrangement may be gathered from 

2c 



434 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



the figure. (The engraver has made the lower end of the condenser 
tube terminate in a point: it should, of course, be open with just a 
slight constriction). 




FIG. S5. — APPARATUS ARRANGED FOR DISTILLATION IN AMMONIA. 

Turn on a gentle stream of water through the condenser, and light 
up the bunsen underneath the flask ; collect 50 c.c. of the distillate, 
remove the Nessler glass and put another in its place. Test the distil- 
late for ammonia ; there should be none present — at most only a trace. 
In the latter case distil over a second 50 c.c. and test it. This must 
contain no ammonia ; should it do so the flask could not have been 
clean, and must be again boiled out with alkaline permanganate. 
Having succeeded in freeing the whole apparatus from ammonia the 
analyses may now be proceeded with. 

Take 10 c.c. of the ten per cent, solution, pour them into a 100 c.c. 
flask, and make up to 100 c.c. with distilled water ; this produces a one 
per cent, solution. Pour away the residue of permanganate left in the 
flask from the blank experiment, add another 150 c.c. of the ammonia- 
free dilute alkaline permanganate solution, and then 5 c.c. of the one 
per cent, solution of the flour or meal. Re-cork and again connect up 
the whole apparatus. Place one of the clean specially graduated Ness- 
ler glasses to receive the distillate. Light the bunsen and place it 
under the flask. Unless care is taken, the solution is liable to boil right 
over into the condenser ; to avoid this, place the bunsen, not in the 
middle, but to one edge of the bottom of the flask, and use only a small 
flame. Distil over exactly 100 c.c. ; remove the Nessler glass, cover 
over with a watch-glass, and turn out the bunsen. A number of ex- 
periments have shown that the whole of the ammonia comes over in the 
first 100 c.c. Time is saved by having two pairs of graduated Nessler 
glasses ; in case there are these, put one of them to receive the distil- 
late, pour out the contents of the flask, and put in the same quantity of 



SOLUBLE EXTRACT, ACIDITY, AND ALBUMINOIDS. 435 

permanganate and 5 c.c. of the one per cent, solution of another sample, 
and set it distilling. 

While the second sample is distilling proceed to estimate the ammonia 
in the first distillate. In the second Nessler glass of the pair put 2 c.c. 
of standard ammonium chloride, and make up to 100 c.c. with ammonia- 
free water. To each of the two acid, by means of a pipette, 1 c.c. of 
Nesslers' solution, cover them over with watch-glasses, and allow them to 
stand for about three minutes. Place the glasses on a tile, look down 
through the liquids and observe which is the darker in colour ; with 
the quantities taken the glass to which the standard solution has been 
added is usually of the darker hue. Take the bent pipette with india- 
rubber ball, squeeze out the air, and put the end in the darker of the 
two solutions ; allow the ball to expand, it thus sucks up some of the 
solution. In this way remove some of the darker solution until, look- 
ing down vertically through the two solutions, they are exactly of the 
same depth of tint. Then read off the height of the liquid in the glass 
and enter in the note-book. This comparison should be made in a good 
light. When apparent equality of tint is obtained, lift both glasses 
up from the tile some three or four inches and again look down. The 
two liquids will then appear lighter in colour, but should be equal 
to each other in depth of tint. This double test assists in forming 
a correct judgment. The glasses may now be washed out and got ready 
for the next analysis. While the one sample is distilling, nesslerise the 
other (i.e., determine the ammonia with Nessler's solution). 

The next step is to calculate the percentage of albuminoids from the 
results obtained. When the Nessler glasses show the same vertical 
depth of tint they contain similar quantities of ammonia ; that in the 
one glass is known, and thus the other may be calculated. Suppose that 
the test glass (i.e., the one to which the standard ammonium chloride 
solution has been added) has been the darker, and that when the two 
are of the same vertical depth of tint the test glass then contains 75 c.c. 
of liquid. As at first there were 2 c.c. of the standard solution in 100 
c.c, there must now be y^ of 2 c.c. — 2 x 0*75 = 1*5 c.c. of standard 
solution. 

Suppose next that the distillate were the darker, and that it had to 
be drawn off until there only remained 85 c.c, then, as 85 c.c contains 
ammonia equal to 2 c.c of the standard solution, 100 c.c. of the dis- 
tillate must have contained ammonia equal to yU* x 2 = 2*35 c.c of 
standard ammonia. 

Having thus found the quantity of ammonia yielded by 5 c.c of a 
one per cent, solution, as expressed in c.c of the standard solution, it 
now remains to calculate the percentage. To find the absolute weight 
of ammonia yielded, multiply the number of c.c of standard solution by 
0*00005, which is the weight of ammonia per c.c. Wanklyn has shown 
that egg albumin, and presumably also the albuminoids of the cereals, 
yield, when distilled in this manner, about 10 per cent, of their weight 
of ammonia ; therefore the weight of albuminoids contained in a sample 
is ten times the weight of ammonia evolved, consequently the next step 
is to multiply by 10. This gives the weight of soluble albuminoids in 
5 c.c of the one per cent, solution, which equals 0-05 grams of the meal 



436 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



or flour. To obtain the percentage, the result must further be multi- 
plied by 2000, or, writing all the factors together, No. of c c. x (0*00005 
x 10 x 2000) = percentage. But the figures included within the brackets, 
when multiplied together, produce unity, so that with the quantities 
taken the number of c.c. of standard solution of ammonia, required to 
produce the same depth of tint when nesslerising, represents the per- 
centage of soluble albuminoids. 

These estimations should appear thus in the note-book : — 

"Estimation of soluble albuminoids by 'ammonia process' in No. 31. 

Usual quantities taken. 

Distillate contained less ammonia than standard. 

With tint equal, standard = 80 c.c. 

2 x 0*80 = 1*6 per cent." 

518. Comparison between Combustion and Ammonia 

Processes. — When worked in the manner described, and with due 
care, the combustion and ammonia processes give fairly concordant re- 
sults. The writer appends the percentages obtained in some experiments 
specially made for the purpose of comparing the processes. The com- 
bustions were made by him personally, the ammonia estimations by his 
assistant, so that not only were the methods different, but each was 
worked by a different person. 





Ammonia 


Combustion 




Process. 


Process. 


r heat 


1-79 


1-63 


,, ... ... 


1-81 


1-81 


,, ... ... 


1-88 


1-89 


55 • • • 


2-17 


1-94 


our 


1-21 


1-23 


55 * * * 


1-30 


1-28 


,, ... ... 


1-40 


1-28 



519. Estimation of Total Albuminoids.— The total albu- 
minoids may also be determined by either method. To make a soda- 
lime combustion, mix 1 gram of the flour with sufficient soda-lime to 
about one-third fill the combustion tube. Collect the evolved gas in 
25 c.c. of decinormal sulphuric acid. Every other part of the operation 
is conducted in the manner already described. The number of c.c. of 
acid neutralised by the evolved ammonia, multiplied by - 0014 x 6*33 x 
100 = the percentage of total albuminoids. 

The ammonia process may also be employed for this determination. 
Carefully weigh out 0*2 grams of the flour, transfer to a 200 c.c. flask, 
and make up to 200 c.c. with a solution containing 5 grams of caustic 
potash to the litre. Shake up thoroughly two or three times during 
half-an-hour ; in this way aO'l per cent, solution is obtained. Take 
5 c.c. of this for the estimation, and proceed exactly as before. The 
number of c.c. of standard ammonia solution found multiplied by 10 
gives the percentage. 

A sample of wheat analysed by the two methods gave 11*37 per 
cent, by the ammonia process, and 10 "63 per cent, by the combustion 
process, of total albuminoids. 



SOLUBLE EXTRACT, ACIDITY, AND ALBUMINOIDS. 437 

520. Modification of Combustion Process for estimation 

Of true Albuminoids only. — The determination of albuminoids by 
the nitrogen combustion process is open to the objection that that por- 
tion of the nitrogen which existed in the grain or flour as nitrates, &o. t 
is also reckoned as nitrogen from albuminoids. It is at times of service 
to estimate the percentage of nitrogen existing as albuminoids or flesh 
formers, as distinguished from other compounds of nitrogen. 

Carbolic acid possesses the property of coagulating the soluble 
albuminoids, and thus rendering their separation from nitrates, &c, 
comparatively easy. Take two grams of the flour or meal and cover it 
in a beaker with a warm four per cent, alcoholic solution of carbolic 
acid : this may be prepared by taking four grams of the pure acid, and 
adding thereto sufficient alcohol (re-distilled methylated spirits) to make 
up the volume of 100 c.c. Let this stand for a quarter of an hour, then 
add a little boiling aqueous four per cent, solution of carbolic acid, stir- 
ring the mixture for about a minute, and then allowing it to cool. 
Wash the solid residue several times by decantation with the cold 
aqueous carbolic acid solution, pouring the washings on to a small filter, 
and finally transfer to it the residue itself ; thoroughly dry the filter 
and residue. Make a soda-lime combustion of both the residue and 
filter, cutting the latter up into shreds and intimately admixing these 
with the soda-lime. The percentage of nitrogen thus obtained, multi- 
2Jlied by 6 33, gives the quantity of true albuminoids. 



438 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



CHAPTER XXIY. 

ESTIMATION OF CARBOHYDRATES. 

521. Estimation of Sugar by Fehling's Solution.— The 

composition and properties of the sugars are fully described in chapter 
VI. It is there shown that maltose is capable of forming a red precipi- 
tate of copper sub-oxide in the reagent termed Fehling's solution, while 
dextrin and starch cause no precipitate. This reaction is not only of 
service in testing for maltose and certain other sugars, but also serves 
the purpose of quantitatively determining the amount of sugar present 
in a solution. 

As before, directions are first given for the preparation of the re- 
agents, and then for the performance of the analytic operation. 

522. Fehling's Standard Copper Solution.— Powder a suf- 
ficient quantity of pure re-crystallised copper sulphate, and dry it by 
pressure between folds of filter paper. Weigh out 69*28 grams, dissolve 
in water, add 1 c.c. of pure sulphuric acid, and make up the solution to 
1 litre. 

523. Alkaline Tartrate Solution.— Weigh out 350 grams of 

pure Rochelle Salt (potassium sodium tartrate), and dissolve in about 
700 c.c. of water. Filter if necessary. Next dissolve 100 grams of 
sticks of pure caustic soda in 200 c.c. of water. If the solution is not 
clear it must be filtered through a funnel fitted with a plug of glass wool. 
Mix the two solutions together, and make up the volume to 1 litre. 

When required for use, these solutions must be mixed together in 
equal proportions ; they then form the original Fehling's solution. This 
solution possessed the disadvantage of changing in character by being 
kept ; and hence the modification in which the Rochelle salt is only added 
to the copper sulphate immediately before the solution is required for 
use. Each c.c. of the mixed solution contains 0*03464 grams of copper 
sulphate, and has been until recently considered equivalent to exactly 
0*005 grams of pure dry grape sugar. 

524. Action of Sugars on Fehling's Solution.— A careful 

investigation has of late been made by Soxhlett of the action on 
Fehling's solution of specially pure specimens of the various types of 
sugars : he finds as a result that the amount of precipitate formed de- 
pends not only on the quantity of sugar present, but also on the degree 
of concentration of the solution, the temperature at which the determi- 
nation is made, and other conditions. Hence great care must be taken 
to always work in precisely the same manner, as it is only by so doing 
that comparative results are obtained. 



ESTIMATION OF CARBOHYDRATES. 439 

Sugar may be determined by Fehling's solution either gravimetrically 
or volumetrically. A description of the gravimetric method is first 
given. The student should commence by practising the estimation on 
cane sugar, as this substance is easily obtained in a condition of purity. 
Cane sugar has no action on Fehling's solution, but when heated gently 
with dilute acid is changed, by hydrolysis, into a mixture of dextrose 
and lcevulose in equal quantities, viz, : — 

C 12 H 22^11 + H 2^ = ^6 H 12^6 + ^6^12^6 
Cane Sugar. Water. Dextrose. Lcevulose. 

Dextrose and lcevulose both act on Fehling's solution, precipitating 
copper sub-oxide, Cu 2 0, in definite quantity. 

525. Gravimetric Method on Cane Sugar. — Procure some 

of the sugar known as Finzel's crystals ; this is the variety of sugar 
sold by the grocer for use with coffee, and consists of large, colourless, 
well-defined crystals of almost pure cane sugar. Select some of these, 
free from extraneous matter, powder them, and dry for a short time in 
the hot-water oven. Make up a one per cent, solution by weighing out 
1 gram of the pure dry sugar, dissolving it in water and making up the 
volume to 100 c.c. Take 50 c.c. of this solution, and add to it 5 c.c. of 
pure fuming hydrocloric acid. For this purpose it is best to use a flask 
graduated at 50 and 55 c.c. Place the flask in a water bath, and heat 
until it reaches the temperature of 68° C. ; this operation should be 
arranged so as to occupy about ten minutes. Next pour the contents 
of the flask into a 100 c c. flask, and add dry sodium carbonate in smalL 
quantities until the solution is neutral, the approach of this point is 
known by the addition of the sodium carbonate causing only a very 
slight effervescence. Test finally with a small strip of litmus paper. 
Cool the flask and make up the contents to 100 c.c. with water. The 
flask now contains a 0'5 per cent, neutral solution of cane sugar con- 
verted into dextrose and lcevulose. Add 25 c.c. of Fehling's standard 
copper solution to the same quantity of alkaline tartrate solution and 
mix the two thoroughly. Take two beakers of about 6 ounces capacity 
and pour into each 25 c.c. of the mixed Fehling's solution. Next add 
to each, 50 c.c. of boiling distilled water that has been boiling for about 
half-an-hour. Stand the beakers in a water bath, the water of which is 
kept boiling by a bunsen ; allow them to stand for seven minutes, 
and then look to see that no precipitate has formed. Should a pre- 
cipitate occur, the Fehling's solution is impure, and is consequently no 
longer fit for use. Next add to each beaker 20 c.c. of the 0*5 per cent, 
sugar solution and replace in the water bath for twelve minutes. The 
precipitated cuprous oxide is best weighed on a counterpoised filter ; 
prepare, therefore, beforehand, two pairs of small Swedish filters, 
trimmed until each one of the pair exactly counterpoises the other, 
when tested in the analytic balance. Arrange a filter-stand with two 
funnel holders, one above the other, so that the filtrate from the upper 
funnel drops into the lower one ; place a beaker underneath for the 
filtrate. Fold one of the pair of counterpoised filters and place it in 
the upper funnel, and filter the copper oxide rapidly from the solution ;, 
the filtrate should still be of a deep blue colour. Examine the filtrate 
carefully in order to see if any traces of the precipitate have found their 



440 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

way through the paper ; if so, re-filter. Being assured that the pre- 
cipitate is being entirely retained by the upper filter, place the other 
one of the counterpoised pair in the funnel underneath, so that the 
filtrate passes through it. Wash both the filters rapidly with boiling 
water and dry both in the hot water oven. The reason for allowing 
the filtrate to also pass through the second paper is- to cause each to be 
in as nearly as possible the same condition, so that it shall still counter- 
poise the first paper after being washed and dried. The filters should 
be dried for twelve hours and then weighed, the counterpoise paper 
being placed on the weight side. 

In order to understand the calculations involved in the estimation of 
sugar by Fehling's solutions, it will be necessary for the student to 
make himself thoroughly acquainted with the properties of the sugars, 
as already described. 

The dextrose and lcevulose, produced by the action of dilute acid on 
cane sugar, as shown in the equation in a preceding paragraph, are 
sometimes grouped together as glucose, or grape sugar ; it is then said 
that one molecule of cane sugar (sucrose) produces, when inverted, two 
molecules of glucose. From the equation it will be seen that the mole- 
cular weight of cane sugar is 342, while that of the glucose formed is 
360. It was formerly supposed that an exact number of molecules of 
CuO of the copper sulphate was reduced to Cu 2 by the sugar ; hence 
we find the statement that two molecules of glucose reduce 10 CuO to 
5 Cu 2 0. Soxhlett's researches, however, show that the reaction is not 
so simple, but, as before stated, varies, being dependent on the degree of 
the dilution of the reagent and other conditions. Different kinds of 
sugar, too, under the same conditions reduce, weight for weight, 
different quantities of CuO to Cu 2 0. Working in the manner directed, 
the reducing power of sugar on Fehling's solution is — 

Cane sugar has no reducing action. 

Glucose 1 gram produces 1'983 grams of Cu 2 0. 

Cane sugar after inversion „ ,, 2 087 „ „ 

Maltose - „ „ 1*289 „ 

The reason why the inverted cane sugar produces more Cu 2 than 
does glucose is, that 1 gram of cane sugar, on inversion, yields more 
than a gram of glucose, the exact quantity being 1*052 grams. When 
only the one variety of sugar is present in a solution the following 
factors may be used for calculating the amount of sugar from the 
weight of precipitated Cu 2 0. 

Glucose, -V = 0*5042. 

Cane sugar after inversion, ^t^ = 0*4791. 

Maltose, tV= 0*7758. 
* 1 289 

Thus, suppose that in the analysis made with the 0*5 per cent, solu- 
tion, the weight of the precipitated Cu 2 was 0*1972 grams, then 
01972 x 0*5042 - 0*0794 of cane sugar. 

Theoretically, in 20 c.c. of the 0*5 per cent, solution there is 0*1 gram 
of sugar ; the results of the analysis give 99*43 per cent, of chemically 
pure sugar. If the estimation were made with perfect accuracy, this 



ESTIMATION OE CARBOHYDRATES. 441 

-would show that the sugar contained 0*57 per cent, of moisture or other 
impurity ; the deficiency is doubtlessly in part due to error of analysis. 
The duplicate estimations made should agree closely. 

When making an analysis of a substance, the composition of which 
is known approximately, a quantity should be taken that contains as 
nearly as can be calculated 0*1 gram of inverted cane sugar, or 02 gram 
of maltose. In case the estimation shows that the amount of sugar 
differs widely from these quantities, a second determination must be 
made in which more or less of the substance is taken. 

526. Volumetric Method of Cane Sugar.— When Fehling's 

solution is intended only to be used gravimetrically, its exact strength 
is not a matter of ^reat importance, but when employed for volumetric 
•estimations its strength must first be accurately determined by titration 
with a standard solution of sugar. For this purpose the 0*5 per cent, 
solution of inverted cane sugar already described may be used. The sugar 
must be added to the Fehling's solution, and not the Fehling's solution to 
the sugar. The sugar solution is therefore placed in a burette, and in 
order that its contents may not get heated during the operation, the glass 
jet is attached by means of a piece of indiarubber tubing about eight 
or ten inches long. The burette may then be placed so as not to be 
vertically over the basin in which the Fehling's solution is being heated. 

Measure out 5 c.c. each of the standard copper and alkaline tartrate 
solutions into a white porcelain evaporating basin ■ add 40 c.c. of well- 
boiled boiling water, and heat the liquid quickly to the boiling point by 
means of a small bunsen flame. In order to test the purity of the 
Fehling's solution, boil for two minutes ; there should neither be a pre- 
cipitate nor any alteration of colour. Next add the sugar solution in 
small quantities at a time, boiling between each " addition. As the 
-operation proceeds, the deep blue colour of the solution disappears ; to- 
wards the end, add the sugar more cautiously, and after each boiling 
allow the precipitate to subside. Tilt the dish slightly over, note whether 
the clear supernatant liquid is still of a blue tint by observing the white 
sides of the dish through it. When the colour has entirely disappeared 
-the reaction is complete. The exact point may be determined with more 
exactitude by means of a dilute solution of potassium ferrocyanide, acidu- 
lated with acetic acid. With a glass rod put a series of drops of this re- 
agent on a white porcelain tile; wash the rod, take out a drop of the clear 
liquid from the dish with it, and add it to one of the drops of the ferro- 
•cyanide • the slightest trace of copper produces a reddish-brown colouration. 

The results of the first estimation must only be looked on as approxi- 
mate, but having thus gained an idea of about how much sugar is re- 
quired, the succeeding ones may be made more quickly, as almost all the 
sugar may be added at one time. Thus if 9*6 c.c. of sugar solution were 
required in the first trial, then in the second, from 8*5 to 9'0 c.c. may 
b>e run in at once, and then the solution added more carefully as the 
■end of the reaction is reached. 

Provided the Fehling's solution is of normal strength, then 
10 c.c. = 0*0500 grams of glucose or invert sugar. 
10 c.c. = 0*0475 ,, „ cane sugar (after inversion.) 
10 c.c. = 0*0741 „ ,, maltose. 



442 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

The difference between the cane sugar and glucose is here again ex- 
plained by the fact than cane sugar produces on inversion more than its 
weight of glucose; 0*0475 gram of cane sugar yields 0*05 gram of glu- 
cose. Working with a 0*5 per cent, solution of cane sugar, each c.c. 
contains 0*005 gram, and 9*5 c.c. contain 0-0475 gram of sugar; 10 c.c. 
of the Fehling's solution should therefore require for its complete re- 
duction 9*5 c.c. of the sugar solution. 

As the Fehling's solution is rarely of the exact strength, its equivalent 
in cane sugar must be noted so as to be used in each determination. 
Suppose the 10 c.c. of Fehling's solution required 9*3 c.c. of the sugar 
solution, then we know that 10-0 c.c. is equivalent to only |4 = 
0*9789 of the respective quantities of different sugars given above. The 
exact strength of the Fehling's solution should be noted on the bottle, 
together with the date when the titration was made; the solution should 
be frequently tested against the solution of pure sugar. The quantity 
of sugar found must therefore be multiplied by 0*9789. An example 
will make this clear. A 0*5 per cent, solution of a commercial sugar 
was tested volumetrically, when 11*4 c.c. of the sugar solution were re- 
quired to completely reduce 10 c.c. of the Fehling's solution. By 
titration 10 c.c. of the Fehling's solution are known to be equivalent to 
0*9789 of 0*0475 = 0*0465 of pure cane sugar; that quantity is there- 
fore present in 11*4 c.c. of the 0*5 per cent, solution. A 0*5 per cent, 
solution contains 0.005 grams of sugar, so that 11*4 c.c. contains 0.0570 
grams of the sugar. As 0*0570 gram of the sample contains 0*0465 
gram of sugar, the percentage of pure sugar in the specimen is 81*58. 
The analysis would appear in the note-book thus : 
" Volumetric determination of pure sugar in a commercial sample of 

cane sugar. 

Inverted and made up to 0*5 per cent, solution. 

11*4 c.c. required to reduce 10 c.c. of Fehling's solution, 

which = 0*0465 gram of pure cane sugar. 

0-0465x100 = 81 . 58 cent of SU gar." 

11*4X0005 r r © 

527. Estimation of Maltose in Wheats or Flours. —The 

method of procedure is much the same as with cane sugar. The prin- 
cipal point is to obtain a solution of the right strength. Assuming that 
an aqueous infusion of wheat contains an average amount of 2*5 per 
cent, of maltose, then 100 c.c. of a 10 per cent, solution of the meal or 
flour contains 0.25 gram of maltose; so that 80 c.c. of the 10 per cent, 
solution are required in order to furnish an approximate amount of 
0*2 gram of maltose. For each quantitative estimation, take 25 c.c. of 
Fehling's solution, 10 c.c. of water, and 80 c.c. of the clear 10 per cent, 
solution of the meal or flour. These quantities give the same degree of 
dilution as those directed to be used in the estimation of cane sugar ; 
proceed exactly as in the determination of that substance. Having 
weighed the precipitate of Cu 2 multiply by the factor 0*7758 ; the 
result is the quantity of maltose in 80 c.c. of a 10 per cent, solution of 
the meal or flour. As 80 c.c. of such a solution contains the soluble 
portion of 8 grams of the meal, the percentage is obtained by multi- 
plying by ^ = 12*5. 



ESTIMATION OF CARBOHYDRATES. 443 

In making this estimation the soluble albuminoids of the grain are 
kept in solution by the alkali of the Fehling's solution. They may if 
wished be removed by boiling and filtering the ten per cent, solution. 
Put about 100 c.c. of the solution in a beaker, take the weight, and then 
boil for about five minutes ; replace on the balance and make up to the 
original weight with distilled water. Filter off the coagulated albu- 
minoids by passing the liquid through a dry filter ; the filtrate is a 10 
per cent, solution, minus the albuminoids coagulated by boiling. 

If maltose is to be determined volu metrically the solution should 
always be first freed from coagulable albuminoids, as described at the 
close of the previous article. Take 10 c.c. of the mixed Fehling's 
solution, add 20 c.c. of water, and run in the clear 10 per cent, solution 
of the meal or flour until the reaction is complete, exactly as was done 
with the inverted cane sugar. * The less quantity of water is added 
because of the maltose solution from the meal or flour being so very 
dilute. 

In case the estimation of maltose is being made in a much stronger 
solution than that obtained by treating a meal with 1 times its weight 
of water, dilute the solution down until it contains approximately about 
one per cent, of maltose, and then work with exactly the same quantities 
as were directed for the inverted cane sugar 0*5 per cent, solution. 

The estimation of maltose in wheats and flours is principally of value 
as a means of judging the amount of alteration which the starch has 
undergone : that a sugar analagous to cane sugar is also present is' 
demonstrated by the experiment quoted in paragraph 270, page 152, in 
which an additional precipitate is obtained as a result of treatment with 
hydrochloric acid. 

528. Estimation Of Dextrin. — Most substances which contain 
maltose contain also dextrin, thus the two are both found in wort pro- 
duced from malt, and also in starch solutions that have been subjected 
to diastasis. Dextrin has no action on Fehling's solution, but by pro- 
longed treatment with an acid is converted into maltose, and ultimately 
into glucose. When maltose and dextrin are simultaneously present in 
a liquid, other carbohydrates being absent, the maltose is estimated 
in a portion as already described; another portion is treated with 
acid, by which both dextrin and maltose are converted into glucose. 
A second estimation of the copper oxide reducing power is then 
made. The weight of precipitate will be found to be considerably 
more than in the first estimation. This is due, in the first place, to the 
fact that glucose precipitates more Cu 2 than does maltose. The mal- 
tose originally present must be calculated into glucose, and the amount 
of precipitate clue to it subtracted from the weight found in the second 
estimation : the remainder is reckoned as glucose produced by the 
hydrolysis of the dextrin ; the percentage may be then obtained by 
calculation. Unfortunately, it is difficult to determine the exact point 
when the whole of the dextrin has been changed into glucose. When 
carefully worked the process is, however, sufficiently accurate for most 
technical purposes, and yields comparative results. The method is 
largely employed for the determination of dextrin in the worts made 
for malt assays. There follows a modification of the process adapted to 



444 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

the determination of dextrin in meals and flours. Having made a 
solution for the determination of maltose, take the same quantity of the 
solution as required for that estimation, viz., 80 c.c, and add to it 2 c.c. 
of dilute sulphuric acid (1 part concentrated acid to 8 of water), stand 
the mixture in a water bath, and heat to boiling for four hours. At 
the end of that time neutralise carefully with caustic potash solution 
(KHO), and proceed to estimate glucose by Fehling's solution precisely 
as before. The excess of glucose in the second solution over that pro- 
duced by the maltose in the first requires to be calculated back to 
dextrin. It must be remembered that glucose is produced from dextrin 
according to the following equation : — 

C 12 H 20 O 10 + 2H 2 = 2C 6 H 12 O 

.Dextrin. Water. Glucose. 



Molecular weight = 324. Molecular weight = 360. 

Therefore, every 360 parts of glucose thus produced represent 324 parts 
of dextrin in the original solution, or 10 of glucose = 9 parts of 
dextrin, so that glucose formed from dextrin x t 9 q = dextrin. As 
already stated, this method must only be looked on as giving results 
sufficiently accurate for technical purposes 

529. Polarimetric Estimations. — In addition to the method 

already described of estimating maltose and dextrin by means of Feh- 
ling's solution, there is a second process in which certain optical proper- 
ties of these bodies are employed in the determination of dextrin, instead 
of hydrolising that substance into glucose by means of dilute acid. This 
particular modification is of special value as a part of the process, to be 
hereafter described, of the estimation of starch, consequently it requires 
careful explanation. 

As has been already stated, the sugars, in common with several other 
bodies, are capable of rotating the plane of polarisation of a ray of light. 
They possess this property not only in the solid state, but also when in 
solution ; further, the amount of rotation is very nearly proportional to 
the degree of concentration of the solution. 

530. Specific Rotatory Power. — The angular rotation of a ray 
of polarised light by a plate of any optically active substance, 1 deci- 
metre (3-937 inches) in thickness, is termed its " specific rotatory 
power." In most substances this has to be obtained by calculation, 
because of the difficulty of getting transparent plates of a sufficient 
thickness. A solution of known strength is prepared, and from the 
rotatory power of this solution the specific rotatory power may be cal- 
culated. The rotatory power of solutions of the same strength may 
vary with the temperature, and also with the solvent employed, hence it 
is necessary to note the strength of the solution at the time of the esti- 
mation, and also the solvent used. The apparent or sensible specific 
rotatory power of a substance is found by dividing the angular rotation 
observed in the polarimeter (a) by the length of the tube in decimetres 
(I usually = 2) in which the liquid is observed, and by the degree of con- 
centration (c), that is the number of grams in 100 c.c. of the liquid. S 
being the specific rotatory power, then the above is represented by the 
formula — 



ESTIMATION OF CARBOHYDRATES. 445 



a 100a 

S = c = 

I x 7ot I x c 



The rotatory power of a substance depends on the nature of the light 
used • as the instrument to be described is one in which the yellow 
monochromatic light of the sodium flame is employed, all numbers given 
will be for light of that description, which is often indicated by the 
symbol Sd. 

In measuring rotatory powers of sugars it has been found convenient 
to take a plate of quartz 1 millimetre in thickness as the standard of 
comparison. According to the latest and most accurate measurements, 
such a plate produces an angular rotation of 21° 44 N = 21*73° for the 
sodium flame (Sd). The strength of the cane sugar solution which, in 
a tube 2 decimetres in length, shall exercise the same rotary power, is 
that equal to 16*350 grams of sugar in each 100 c.c. of the solution. 

c 100x21*73 aa'AKo 

Sd = 7T^—„ = 66-45 

2x16-350 

as the specific rotatory power of cane sugar. 

All sugars do not rotate the plane of polarisation in the same direc- 
tion : thus some twist it to the right, or in the direction of the hands of 
the clock, others twist it towards the left. The terms dextro- and loevo- 
rotation are applied to the right-handed and left-handed rotation respec- 
tively. Also the symbol + is used to represent dextro- and — to 
represent lcevo-rotation. The specific rotatory power of the substances 
of importance in connection with the chemistry of wheat and flour is 
appended : 



Substance. 

Cane sugar 


Formula. 


Specific 
Rotatory Power. 

+ 66-5° 


Maltose 


12 22 -11 


+ 139-2° 


Dextrose 


^6^12^6 


+ 51-9 


Lcevulose 


C 6 H 12°6 


- 98° at 15° C. 


Invert sugar 
Dextrin 


2C 6 H 12 6 

^6 H 10^6 


-23-05° at 15° C. 
+ 193° 



531. The Polarimeter. — We will next describe one of the forms 
of the polarimeter, and for that purpose will select the " J ellet-Cornu 
Polarimeter," or " Saccharimetre a Penombres," as manufactured by 
Duboscq, of Paris. This instrument is simple in construction, well 
made, and of reasonable price. 

Figure 89 is an illustration of the instrument and the bunsen used for 
the production of the sodium flame. When using the polarimeter it is 
well to work in a room from which all light other than that of the 
sodium flame is excluded. The instrument consists essentially of a 
tripod support, carrying a horizontal frame in which is placed the tube 
filled with the solution under examination, and having at the one end, 
A, the polarising prism, and at the other the analyser, together with a 
small telescopic arrangement, used as an eye-piece. 



446 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 




FIG. 89.— JELLET-CORNU POLARIMETER. 

E 



B gMlji 1,11 



^M 



FIG. 90. — POLARIMETER TUBE. 



ESTIMATION OF CARBOHYDRATES. 



447 



532. Polarimeter Tubes. — These tubes are made of brass, lined 
with tin, and are exactly 20 centimetres in length from end to end 
inside the caps. The left-hand illustration, Figure 90, represents the 
tube with the ends screwed on ; the other shows the tube in section. 
Each cap contains a glass plate which fits accurately to the end of the 
brass tube ; above the glass plate is a washer of leather ; on screwing 
on the cap this washer exerts an equable pressure on the glass plate, 
and so makes a water-tight joint. The mistake must not be made of 
placing the washer inside instead of outside the glass plate. When 
using the tube it is first cleaned, then dried or rinsed with a few drops 
of the liquid under examination ; one of the caps is next screwed on. 
The tube is then filled with the solution, any bubbles are allowed to 
escape, and then the second glass plate is slidden over the end and 
screwed tight by means of the cap. If properly filled the tube should 
contain no air, neither should it leak. If there should be any tendency 
to leakage it may be prevented by very slightly greasing the ends of the 
tube. It will be evident that such a tube contains a layer of the liquid 
exactly 20 centimetres in length. 

533. Polarimeter Tube, with Thermometer, — Figure 91 

shows a polarimeter tube of slightly different construction : it is, in the 
first place, lined with glass, and is 22 instead of 20 centimetres long. 
On the top there is a tubulure, by which a thermometer is inserted in 
order to determine the temperature of the solution at the time the 
estimation is made. The use of this particular form of tube will be 
described hereafter. 




FIO. 91. — FOLARIMETER TUBE, WITH THERMOMETER. 



448 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

534. Verification of Zero of Polarimeter. — The first operation 

to be performed in starting work with a new polarimeter is to verify 
the zero of the graduated scale of the instrument. The Jellet-Cornu 
polarimeter is provided with two scales, both of which are engraved on 
the circular disc at the front of the instrument. The upper scale is one 
of sugar degrees, the lower is graduated into angular degrees, namely, 
90° to the right angle. The vertical arm which shows in the figure 
traversing the front of the disc in a vertical direction is provided with 
a Vernier scale at each end. The edge of the disc is cut into teeth and 
gears into a small pinion, actuated by the milled head P, this, on being 
twisted, moves the eye-piece and analysing prism, together with the 
Vernier scales. To make this verification of the zero, commence by 
placing some fused sodium chloride in the platinum spoon of the bunsen 
lamp, then light the bunsen, and turn the spoon into the flame so that 
an intense yellow light is produced. Arrange the axis of the instru- 
ment in the direction of the flame, so that on looking through the eye- 
piece a brilliant yellow field is seen. Next fill one of the 20 centimetre 
tubes with distilled water, and put it in its proper position in the 
polarimeter. Place the zero of the Vernier in coincidence with that of 
the scale, and look carefully through the instrument in order to see 
whether both halves of the field are equally illuminated. Turn the 
milled head P very slightly in either direction, one half of the field 
becomes dark, and the other lighter. Now focus the eye-piece by draw- 
ing it out or pushing it in until the vertical line, dividing the two halves 
of the field, is sharply defined. In performing this operation see that 
neither of the milled heads of the instrument are touched. Having 
focussed the eye-piece, turn P back again until the two halves of the 
field are equally illuminated : note the position of the Vernier and see 
whether it coincides with the zero of the scale. (Por reading the Ver- 
nier a small microscope is provided ; this is carried on a moveable arm 
attached to the eye-piece). Should the two agree, once more displace P 
and again bring it back to the position in which the two halves of the 
field are equally bright, and read the Vernier. Observe whether the 
two readings of the zero are alike. If the zero of the instrument is 
found correct, well and good, but if not, turn P until the zero of the 
Vernier is exactly over that of the scale ; then turn the milled head, 
marked O, until the two halves of the field are of the same depth of 
tint. Make this adjustment most carefully ; when once made, the 
milled head must not be again moved or the polarimeter will be thrown 
out of adjustment. 

535. Method of Reading with Vernier. — To those not ac- 
customed to the use of the Vernier for the purpose of accurately reading 
graduations on instruments of exactitude, a few words of explanation of 
that device will be acceptable. The Vernier is a small scale which slides 
over the graduations of the principal scale of the instrument. On the 
Vernier a length equal to nine of the graduations on the fixed scale is 
divided into 10 equal parts. As a consequence each division on the 
Vernier is exactly nine-tenths of each on the fixed scale. Bearing this 
in mind, let us see how the Vernier is used in actual work. Suppose 
that with the polarimeter a sugar solution is placed in the instrument 



ESTIMATION OF CAEBOHYDRATES. 449 

and the analyser turned until the two halves of the field are illuminated 
equally. It now becomes necessary to read off the number of degrees 
through which the analysing prism has been rotated. On looking at 
the scale we find that the zero of the Vernier is between, say 94 and 95 
degrees. Look along the Vernier scale in the direction of the 95 until 
one of the graduations on the Vernier exactly coincides with one on the 
fixed scale. If this graduation on the Vernier is 7 from the zero, then 
the accurate reading of the polarimeter is 94*7°. In fact, whatever 
number graduation on the Vernier coincides with one on the other 
scale, the number of that particular Vernier graduation represents the 
fraction of a degree in decimals. This will be seen to be the case on 
reflection. A fuller explanation of the Vernier may be found in Ganot's 
" Physics." 

536. Polarimetric Estimation of Cane Sugar. — As a 

matter of practice the student will do well to make some polarimetric 
estimations on pure cane sugar. For this purpose powder finely some 
clean Finzel's crystals, and dry for a short time at 100° C. Weigh out 
exactly 16-350 grams of the sugar, dissolve in distilled water and make 
up to 100 c.c. Fill one of the two decimetre tubes with this solution, 
which must be perfectly clear and transparent. Prepare the polarimeter 
for working and introduce the tube. By means of the milled head, 
rotate the analyser to the right until the point is reached at which the 
change from illumination of the one side of the field to that of the other- 
occurs with great sharpness. Turn the milled head very slowly, and 
observe carefully the exact point at which equal illumination is reached. 
Read off the number of degrees by means of the Vernier on the upper 
scale ; then shift the analyser, once more bring it back to the neutral 
point, and again read. The two readings should agree to the tenth part 
of a sugar degree. If the sugar be absolutely pure, and the operation 
be made correctly, the reading should be precisely 100. This signifies 
that the sample under examination contains exactly 100 per cent, of 
pure cane sugar. Similarly, if the polarimeter stood at 9 7 -3, we should 
state that the sample contained 97*3 per cent, of pure sugar. 

537. Polarimetric behaviour of inverted Oane Sugar.— 

It has been already stated that the operation of treating cane sugar 
with an acid and so causing it to precipitate cuprous oxide from 
Fehling's solution, is termed "inverting" the sample. The reason is, 
that a solution of sugar thus treated rotates the plane of polarisation to 
the left instead of to the right. Take a flask having two marks on the 
neck, one at 50 and the other at 55 c.c, fill up to the 50 c.c. mark with 
the sugar solution and then add 5 c.c. of pure fuming hydrochloric acid. 
Next heat the flask in a water bath until its contents have acquired a 
temperature of 68° C. ; this operation should be so arranged as to 
occupy about ten minutes. Cool the flask by immersion in cold water. 
Fill the 22 centimetre tube with this solution ; insert the thermometer, 
note the temperature and read the amount of rotation, which will be 
left-handed, with the polarimeter. The reason for having a tube 22 
centimetres in length will now be evident ; the addition of 6 c.c. of acid 
to 50 c.c. of sugar solution will have diluted the solution to j-± of its 
2 D 



450 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

former volume. When the reading is taken in a 22 centimetre tube 
that also is ^~ of the length of the 20 centimetre tube, consequently a 
depth of liquid equal to 20 centimetres of the sugar solution before in- 
version is looked through. Working in this manner, no calculation is 
necessary for the dilution resulting from the addition of the acid. 
Careful observation has shown that a solution of cane sugar which 
before inversion gave a right-handed rotation of 100°, gives after that 
operation a rotation of 39° to the left, provided the temperature of the 
inverted solution is 10° C. The plane of polarisation is threfore, by the 
operation of inversion, rotated through 139° on the sugar scale. As 
has been stated, inversion produces from the one molecule of cane sugar 
two molecules of glucose, one each of dextro-glucose and loevo-glucose. 
This latter body has a diminished rotatory power at high temperatures, 
and hence it becomes necessary to read the temperature at which the 
observation is made. The rate of diminution is 1° or division for each 
increase of 2° C. At 0° C. the change resulting from inversion amounts 
to 144 divisions ; for any higher temperature the value is found by 

Suppose that in the test experiment with pure cane sugar the polari- 
metric reading was - 36, and that the thermometer registered 16° C, 
then to find the equivalent reading at 0° C. all that is necessary is to add 

- (in this case = 8) to the observed reading of total number of divisions, 

A 

the result is the reading for 0° C. ; giving 144 in the experiment being 
considered, which is the theoretically correct figure. In event of the 
sugar containing 10 per cent, of moisture, the right hand reading would 
only amount to 90 ; similarly, the reading after inversion and calcula- 
tion to 0° C. would amount to exactly t 9 q of 144 divisions. If, on the 
other hand, some substance, as dextrose, were present which is not 
capable of inversion by the method adopted, then the left-hand reading 
would be less than the theoretical amount for cane sugar. Thus the 
polarimeter affords not only a means of observing the percentage of 
sugar present in a sample, but also gives valuable indications as to the 
nature of the impurity. 

538. Polarimetric determination of Dextrin and. Mal- 
tose. — We must next turn our attention to the method of using the 
polarimeter for estimating the amount of dextrin in a liquid containing 
both dextrin and maltose. It may happen that the liquid is not suffi- 
ciently clear to be transparent in a layer of so much as 20 centimetres ; 
it must then be clarified by treatment with animal charcoal in the fol- 
lowing manner : add to the solution, in a flask, about one-fifth of its 
volume of powdered, recently ignited, pure animal charcoal. Shake up 
vigorously for a few minutes, and pass through a dry filter. Return 
the filtrate to the paper until it comes through perfectly clear. Should 
the liquid contain any coagulable albuminoids they should next be re- 
moved by heating a known weight of the liquid for a few minutes in 
the hot water bath, making up the lost weight with distilled water and 



ESTIMATION OF CARBOHYDRATES. 451 

then filtering. For the polarimetric reading, as concentrated a solution 
as possible should be taken, and the observation made in the 20 centi- 
metre tube. After reading with the polarimeter, dilute down to the 
right strength, and estimate maltose by Fehling's solution. 

Knowing the quantity of maltose present, in order to calculate the 
proportion of the polarimetric effect due to dextrin, the amount of 
rotation due to maltose must be calculated. On multiplying the number 
of grams of maltose in 100 c.c. of the solution by 2*71, the result is the 
angular rotation due to the maltose. Subtract this number from the 
observed angular rotation, and the remainder is the angular rotation 
due to dextrin. This angular rotation, on being divided by 3-86, or 
multiplied by 0-259, gives the grams of dextrin in 100 c.c. of the liquid. 
From these data the percentage of dextrin and maltose in the original 
substance may be calculated. 

It will be of interest to mention that the most recent determinations 
hy O'Sullivan gave, for dextrin, Sd = 200*4°. His factors for cal- 
culating dextrin polarimetrically are 2-78 instead of 2-71, and 4-008 for 
the multiplier 3 '86. 

As an illustration of the polarimetric estimation of dextrin the 
following example of the analysis of a sample of wheat germ is given. 
A 10 per cent, solution of the substance was made with cold water, 
filtered, shaken up with animal charcoal, and again filtered until clear. 
The clear solution was weighed in a beaker, raised to 100° C, in the 
water bath, made up to original weight, and filtered from the coagulated 
albumin. The reading with the polarimeter was 2 '00° to the right. A 
maltose estimation was made with 20 c.c. of the solution to 25 c.c. Feh- 
ling's solution and 50 c.c. of water. The resulting precipitate was in 
this instance converted by ignition into cupric oxide (CuO) and weighed 
as such, then — 

Wt. of CuO -0-1515 x 0-7313 = 0-1107 gram of maltose in 20 c.c. of 
10 per cent, solution. 

0*1107 x 5 = 0-5539 gram of maltose in 100 c.c. 

0-5539 x 10 = 5*539 per cent, of maltose in the substance. 

Then, 0*5539 x 2-78 = 1-52 = angular rotation due to maltose. 

Total angular rotation, 2 — 1-52 =0*48 = angular rotation due to dex- 
trin. 

0-48 x 0*259 = 0*124 gram of dextrin in 100 c.c. 

0*124 x 10 = 1*24 per cent, of dextrin present in the substance. 

539. Estimation Of Starch. — This estimation may be roughly 
made by retaining for examination the whole of the washings from the 
gluten test for wheat or flour. For this purpose wash the dough in 
small quantities of water at a time until the water remains clear, the 
washings being poured into a large beaker. Stir the starch and water 
thoroughly together, and then strain through a piece of fine silk into a 
second clean beaker in order to recover any fragments of gluten that 
may possibly have been in the first instance forced through the silk. 
Having washed the whole of the starch through the silk, stand the 
beaker aside in order to allow the starch to subside. Counterpoise a 
pair of filters and arrange them in funnels one under the other, so that 
the lower receives the filtrate of the upper. Remove the lower funnel 



& 



452 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

and pour the supernatant liquid from the starch on to the upper filter ; 
as soon as the nitrate runs clear, replace the second funnel and con- 
tinue the filtration, finally rinsing the whole of the starch on to the 
filter; wash with distilled water and dry, first for a few hours at 40° C, 
and afterwards in the hot-water oven. The reason for first drying at a 
low temperature is to prevent the gelatinisation of the starch ; this pre- 
liminary drying may generally be done on the top of the hot-water oven. 
The counterpoise filter may, of course, be dried direct in the oven, and 
at the end weighed against the starch and filter. This treatment gives 
the weight of starch cells of the wheat or flour. These, it must be re- 
membered, contain a certain quantity of starch cellulose. 

540. Estimation of Soluble Starch by Conversion into 

Dextrin and Maltose. — For more refined estimations the method of 
first converting the starch into dextrin and maltose, and then deter- 
mining those bodies, is preferable. O'Sullivan gives, in the " Journal of 
the Chemical Society" for the year, 1884, a description in detail of his 
method of making such estimations. The method is based on first re- 
moving dextrin, maltose, and other soluble bodies from the substance 
by the use of water and other solvents, then converting the starch into 
dextrin and maltose by the action thereon of malt diastase, and then 
estimating the dextrin and maltose by Fehling's solution and the polari- 
meter. The following special reagents are necessary : 

54 1 . Alcohol. — This reagent is required absolutely free from water, 
and also mixed with water indifferent proportions. "Absolute "or 
water-free alcohol may either be purchased or prepared in the following 
manner : — Take two quarts of the best methylated spirits, add thereto- 
about half its weight of recently and thoroughly burnt quicklime, shake 
up vigorously two or three time a day for three or four days. The 
quicklime will dehydrate the alcohol, by combining with the water 
present, to form slaked lime (calcium hydrate). The alcohol must next 
be separated from the lime by distillation. For this purpose arrange a 
glass flask, or tin or copper vessel of sufficient size, in a large saucepan 
to be used as a water bath. Fit a cork with leading tube to the neck 
of the flask, and connect this up to a condensing worm, provided with a 
copious supply of water. Be sure that all joints are perfectly air tight. 
Fill the water bath with brine, and make arrangements for securing the 
flask so that, as it becomes lighter by the evaporation of the spirit, it. 
shall not capsize. Pour off the clear alcohol from the lime into the 
flask, connect up the whole of the apparatus, and raise the bath to the 
boiling point by means of a bunsen. Collect the distilled spirit in a 
dry stoppered bottle. It must be remembered that alcohol is highly 
inflammable, and therefore every care must be taken to prevent an 
accident through fire. The lime used for the desiccation of the alcohol 
will still contain a considerable quantity of spirit ; this may in great, 
part be recovered by pouring the whole on to stout calico and squeezing 
as much as possible of the spirit out. 

Absolute alcohol has a specific gravity of 07937 at 15° C. The 
percentage of water is usually obtained by observing the specific gravity 
by means of a hydrometer. This is a glass instrument consisting of a 



ESTIMATION OF CARBOHYDRATES. 453 



weighted bulb and stem carrying a scale ; the hydrometer, on being 
23laced in a liquid, floats higher or lower according to its density. The 
specific gravity of water is often reckoned, for convenience, at 1000 ; 
absolute alcohol is then said to have a density of 793*7. A hydrometer 
should be procured from the instrument makers marked in single 
degrees from 750 to 1000. 

Cool down some of the distilled alcohol to 15° C, and pour out into a 
hydrometer jar. (This is a tall glass vessel in which the instrument 
can just float.) Introduce the hydrometer, and observe the density of 
the liquid, should this be from 795 to 800 the alcohol may be considered 
for practical purposes, absolute. Mixtures of alcohol and water of the 
following densities are also required, 820, 830, 860, 880, and 900 
degrees. These may be prepared by adding water to methylated spirit. 

Methylated spirit has itself a density of about 820, and, when re- 
distilled, may be used when that strength is directed. The strength of 
solutions of other degrees of specific gravity is given below. 

Specific Absolute 

gravity. Alcohol, 

at 1 5 "5° C. by volume, o/o 

0-8599 81-44 

0-8299 91-20 

0-8209 93-77 

0-7999 98-82 

0-7938 100-00 

In order to obtain diluted spirits of the other gravities required, 
water may be added in the requisite proportion to methylated spirit. 
As alcohol and water, on being mixed, contract in volume (i.e., 50 c.c. 
of alcohol and 50 c.c. of water produce less than 100 c.c. of the mixture), 
the amount of water to be added to the methylated spirit to produce 
each degree of dilution cannot be calculated with absolute exactness, 
but still sufficiently near for present purposes. Knowing that alcohol 
of sp. gr. of 820 contains 93 '77 of alcohol and 6*23 of water, the 
quantity necessary to be added is determined by the following 
formula : — 

A = percentage of absolute alcohol in stronger spirit. 
a= ,, ,, ,, weaker. 

W= ,, water stronger. 

w= ,, „ weaker. 

Q = quantity of water to be added to 100 c.c. of the lower sp. 
gr. spirit to produce the higher sp. gr. spirit. 
Then A x w 

Q = W. 

x a 
From this formula it is found that to 100 c.c. of 820 spirit the 
following approximate quantities of water must be added to produce the 
spirits of correspondingly higher gravities — sp. gr. 830 — 3 c.c, 870 — 
21 c.c, 900—43 c.c. 

542. Diastase. — Take 2 or 3 kilograms (5 or 6 lbs.) of finely 
ground pale barley malt, add sufficient water to completely saturate it, 
and when saturated to slightly cover it. Allow this mixture to stand 



Specific 


Absolute 


gravity. 


Alcohol, 


at 15-5° C. 


by volume, o/o 


1-0000 


o-oo 


0-9499 


41-37 


0-9198 


57-06 


0-8999 


65-85 


0-8799 


73.97 


order to obtain 


diluted spir 



454 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

for three or four hours, and then squeeze as much as possible of the 
solution out by means of a filter press. Should the liquid not be bright 
it must be filtered. To the clear bright solution, add alcohol of sp. gr. 
830 as long as it forms a precipitate, and until the liquid becomes 
opalescent or milky. Wash this precipitate with alcohol of sp. gr. 
860-880, and finally with absolute alcohol. Press the precipitate 
between folds of cloth, in order to dry it as much as possible. Then 
place the precipitate in a dish, and keep under the exhausted receiver 
of an air-pump, together with a vessel containing concentrated sulphuric 
acid, until the weight becomes constant. The kind of air-pump known 
as a mercury sprengel pump is best fitted for this purpose. Prepared 
and dried in this manner, diastase is a white easily soluble powder, 
retaining its activity for a considerable time. Store the substance in a 
dry stoppered bottle and keep in a cool and dry place. 

543. Method of Performing Analysis.— The analytic opera- 
tion is performed in the following manner : weigh out accurately 5 grams 
of the finely ground meal or flour ; introduce this quantity into a wide 
necked flask with a capacity of 100 to 120 c.c. (a four ounce conical 
flask will be found most convenient). Add just sufficient alcohol of 
sp. gr. 820 to just saturate the flour, and then 20 to 25 c.c. of ether. 
Cork the flask, and set aside for a few hours, shaking up occasionally. 
Decant the clear ethereal solution through a filter, wash the residue 
three or four times with fresh quantities of ether, pouring the washings 
each time on the filter. To the residue add 80 to 90 c.c. of alcohol of 
sp. gr. of 900 ; re-cork the flask, and maintain the mixture at a tempera- 
ture of 35° to 38° C. for a few hours, shaking occasionally. When the 
alcohol solution has become clear, decant it through the filter, used for 
filtering the ether solution, and wash the residue a few times with 
alcohol of the strength and temperature directed above. Wash the 
residue in the flask, and any that may be on the filter, into a beaker 
capable of holding 500 c.c, and nearly fill the beaker with water. In 
about twenty-four hours the supernatant liquid becomes clear, when 
gradually decant through a filter. Wash the residue repeatedly with 
water at 35° to 38° C, and then transfer to 100 c.c. beaker. Take the 
filter from the funnel and open out the paper on a glass plate, and 
remove every particle by means of a camel-hair brush cut short, and a 
fine spouted wash-bottle. Having thus transfered the whole of the 
residue, the beaker should not contain more than 40 to 45 c.c. of liquid. 
Boil for a few minutes in the water-bath, care being taken to stir well 
in order to prevent " balling," or unequal gelatinisation of the starch. 
After this, cool down the beaker still in the bath to 62° to 63° C., and 
0-025 to 0*035 gram of diastase dissolved in a few c.c. of water. In a few 
minutes the whole of the starch is dissolved, and a trace of the liquid 
gives no discolouration with iodine. Continue the digestion for about an 
hour, then raise the bath to the boiling point, and boil for eight or ten 
minutes. Pour the contents on to a filter, and receive the filtrate into a 
100 c.c. measuring flask; carefully wash the residue with small quantities 
of boiling water at a time. Cool the flask to 15 '5° C, and make up its 
contents to 100 c.c. with distilled water. Should the washings and 
solution exceed 100 c.c. they must be evaporated down to that amount. 



ESTIMATION OF CARBOHYDRATES. 455 

Take a polarimetric reading of this solution in the 20 centimeter 
tube. Five c.c. of the solution is a convenient quantity to take for the 
estimation of maltose. This is rather a small quantity to measure accu- 
rately; it may if wished be weighed instead, or 25 c.c. may be taken 
and diluted down to 100 c.c. with water; 20 c.c. of the diluted solution 
may then be taken and added to 25 c.c. of Fehling's solution and 50 c.c. 
of water. Proceed as before described with the estimates, and calculate 
the quantity of maltose from the weight of precipitated Cu 2 0. Calcu- 
late the relative percentages of dextrin and maltose in the usual manner. 
Starch produces its own weight of dextrin and |~|f- = 1*0546 its weight 
of maltose. To obtain the weight of starch from the dextrin and 
maltose it produces, the weight of the dextrin must be added to that of 
the maltose, divided by 1*0526 or multiplied by 0*95. These calcula- 
tions will be rendered clear by the study of the following example taken 
from O'Sullivan's paper. 

In the analysis of a sample of white wheat, 4*94 grams were taken. 
The 100 c.c. solution had an optical activity equivalent to 8*52° for Sd, 
and contained 2*195 grams of maltose. 

2-196 x 2*78 = 6*10°, angular rotation due to maltose. 8*52°--6*10° = 
2*42°, angular rotation due to dextrin. ^8 = '605 gram of dextrin 
in 100 c.c. 

Maltose, 2*196 = starch, 2*196 x 0*95 = 2*086 
Dextrin, 0*605 = starch, 0*605 



Total starch = 2*691 



2*691 x 100 = 54*47 per cent, of starch present. 
4 T 94 
A duplicate analysis on 6*009 grams differed only by 0*03 per cent. 

544. Estimation Of Cellulose. — The student already knows that 
cellulose has the same chemical composition as starch, but that it differs 
from that body in being insoluble in boiling water. The cellulose or 
woody fibre of grain has been estimated at about 10 per cent, of the 
whole ; but of this much is soluble in the digestive secretions of animals, 
particularly those which ruminate, therefore an estimation of cellulose 
simply is not the one most valuable to the chemist whose investigation 
is made for the purpose of determining the food value of a substance. 
What for this purpose should be ascertained is that percentage of the 
grain or flour which is ejected from the alimentary canal in an unaltered 
condition. A process is therefore selected which is somewhat similar 
to the digestive action which proceeds in the stomach, this action being- 
imitated by alternate treatment with dilute acid and alkali. 

545. Special Reagents necessary.— The first of these is a 5 

per cent, solution of sulphuric acid. In a small beaker, weigh out 100 
grams of the concentrated acid, and make up to two litres. In the 
next place prepare a 1 2 per cent, solution of caustic potash, by weighing 
out 240 grams of the pure dry sticks, dissolving, and making up to two 
litres with water. It is important that 20 c.c. of the acid solution 
should be approximately neutralised by 10 c.c. of the alkali. 



456 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

546. Mode Of Analysis. — Take 5 grams of the meal or flour, and 
mix them thoroughly with 150 c.c. of water in a beaker. Stand this 
in a hot-water bath and raise to a boiling heat in order to effect the 
gelatinisation of the starch ; stir frequently with a glass rod ; add 50 
c.c. of a 5 per cent, solution of sulphuric acid, and continue the boiling 
for an hour, stirring occasionally and maintaining the volume at 
200 c.c. by adding from time to time a little water. (The proper 
■volume should be indicated by a mark made with the diamond on 
the outside of the beaker. The acid will by this time have con- 
verted the starch, and also a portion of the cellulose, into sugar. 
To this solution, next add 50 c.c. of the solution of caustic potash : this 
quantity will neutralise the free acid, forming potassium sulphate ; and 
will leave an excess of alkali in the solution approximately equivalent 
to the amount of acid first used. Again boil in the hot-water bath for 
an hour, adding water to supply that lost by evaporation, and occasion- 
ally stirring. At the end of this time, dilute with cold water, stir, and 
allow the residue to subside. Wash by decantation, using large quan- 
tities of tap water (provided it is absolutely free from sediment), pour- 
ing as little as possible of the residue on to the paper. Stout well- 
made quantitative filters of about eight or ten inches diameter should 
b>e employed : the author uses those of Schweniker's make. Next 
transfer the residue to the filter, and wash once with dilute hydrochloric 
acid, in order to dissolve any calcium carbonate that may be precipi- 
tated from ordinary water by the potash. Then wash, with distilled 
water, till free from acid, and allow the filter to drain. While still 
wet, remove the filter paper from the funnel, carefully spread it out flat 
on a sheet of glass, and with a wash bottle and short camel's hair-brush, 
transfer the whole of the residue to a counterpoised glass dish, dry in 
the hot-water oven and weigh. The dry residue multiplied by 20 gives 
the weight of indigestible fibre in the sample. 



BREAD ANALYSIS. 457 



CHAPTER XXV. 

BREAD ANALYSIS. 

547. Having described the methods to be employed for the deter- 
mination of the various constituents of wheat and flour, a short descrip- 
tion must now be given of bread analysis. 

Many of the properties by which good bread is distinguished from 
bad scarcely come within the range of purely chemical analysis. Among 
these are the colour, texture, "piling," odour and flavour of the crumb, 
and the colour and thickness of the crust. In the kind of bread known 
technically as " crumby " bread the colour and texture of the joint be- 
tween two loaves is to be observed. The analyst, in reporting on bread, 
should examine the loaf so far as the above characteristics are concerned, 
and include his opinion on the same in his report. In judging each he 
may adopt the plan of employing a series of numbers, say 1 to 10, and 
using the lowest number for the worst possible grade, and the highest 
for the very best. Or he may use instead the terms V. B., very bad; 
B, bad ; I, indifferent ; M, moderate ; G, good ; V. G., very good ; E, 
excellent. In either case the same term must, so far as is possible, be 
applied to the same grade of quality, whether of texture, colour, or 
other characteristic. 

548. Colour. — The baker's use of this term involves a contradic- 
tion ; it is the custom of the trade to speak of a loaf as " having no 
-colour " when a dark brown, while in the purest white loaf the colour 
is said to be " high." This is of course exactly opposite to the correct 
use of these terms, for white is strictly no colour, while a yellow or 
brown body is strongly coloured. It would be a better plan if the 
respective terms were "lightly coloured" and "strongly or deeply 
■coloured." Judging colour by itself alone, the loaf should be a very 
light yellow or creamy tint, approaching almost to whiteness. This 
colour is selected because the writer is of opinion that judging bread by 
the eye alone, the slightest yellow hue is more agreeable than an ab- 
solute snowy whiteness. The latter, perhaps from its frequent associa- 
tion with absence of flavour, is unpleasant. 

It must be remembered that colour, &c, are matters of individual 
taste and opinion, and therefore that each individual has his own 
standard of comparison. In forming a judgment one naturally most 
appreciates that in accordance with one's own standard ; it does not 
necessarily follow that such judgment shall absolutely agree with that 
of another person. It is a well-known fact that in different localities 
the standard of taste in these matters varies. 



458 CHEMISTRY OP WHEAT, FLOUR, AND BREAD. 

549. Texture- — The texture of a loaf is best observed by cutting 
it in two with a very sharp knife. There should be an absence of large 
cavities and also of dry lumps of flour. The honeycombed structure of 
the bread should be as even as possible. The bread should not break 
away easily in crumbs ; but should be somewhat firm. On being gently 
pressed with the finger the bread should be elastic, and should spring 
back without showing a mark on the pressure being removed. 

550. Piling. — In the south of England, by a well-piled loaf is 
understood one that has risen well, both in the dough stage and after 
being placed in the oven. The " well-proved loaf " is another phrase 
having there substantially the same meaning. It almost goes without 
saying that in judging the quality of a loaf the baker likes it to be as 
large as possible. Such an opinion is a sound one where size of the loaf 
is combined with evenness of texture, and is not the result of the presence 
of large cavities in the bread. The opposite of a well-piled loaf is a 
heavy one ; hence this matter of the piling of a loaf is of importance. 
The loaf which in this particular looks the best is that which is most 
digestible and wholesome. 

The trade terms, Pile and Proof, are used in very different senses in 
different localities ; thus, a number of bakers use this term to refer to 
the size of a loaf : with them a well proved loaf is a well risen one. On 
the other hand, it has been explained to the author, that two loaves 
may have risen equally well, and yet the one be far better proved than 
is the other. The well proved loaf is, under these circumstances, viewed 
as that in which fermentation has proceeded until the flavour of the 
bread (the bouquet, if the term may be borrowed,) has developed to the 
greatest perfection. The well proved loaf will be sweet and nutty in 
flavour, and have all the characteristics of being thoroughly cooked ; 
the badly proved loaf will be lacking in flavour, and have what, for want 
of a better expression, may be called a "raw" taste. Undoubtedly 
this use of the term " proving " refers to a difference which does exist in 
the two loaves ; a difference which in all probability is due to the more 
or less perfect peptonising action of the yeast on the albuminoids during 
fermentation. Mr. W. A. Thorns has been kind enough to inform the 
author as to the exact sense in which these terms are used in Scotland, 
and as no man can speak with more authority on this subject, his letter 
is quoted at length : — " By a well piled loaf we do not understand a loaf 
well risen. Pile is the gloss of the outside skin, or crumb of close 
packed bread, and the more unbroken the skin the more silky in feel 
and glossy in sheen, the higher we rank the pile. Undoubtedly a well 
piled loaf must also be a well risen loaf. They have that in common, 
but a well risen loaf may be ragged, broken-skinned and dark, without 
being over proved ; such a loaf we call coarse, and say it has a bad or no 
pile. Proof, in dough or baked bread, refers to volume or size. These 
qualities, proof and pile, are due to the same factor, carbon dioxide 
acting on and distending the gluten, and it is the condition of the gluten 
at the time in the oven, when the dough is passing into bread, that 
determines the pile. The condition, good or bad, of the gluten in this 
transition state may be due to the condition of the flour, the proportion 
of gluten it contains, or to the action of the yeast and its by-products 



BREAD ANALYSIS. 459" 



on the gluten during the entire fermentation. Unhealthy yeast will 
produce an abnormal proportion of acids, and acids render gluten first 
friable and then soluble. At the friable stage bread may be high, badly 
shaped, dark and ragged, but deficient in pile." 

55 1 . Odour. — This is best judged by pulling a loaf open and burying 
the nose deep in the cleft. The bread should have a nutty, sweet smell; 
this denotes the highest degree of excellence so far as this quality is 
concerned. There may be an absence of smell, or what is perhaps most 
forcibly described as a mawkish and damp odour ; these belong to the 
indifferent stage. The bread may smell sour ; in which case an un- 
favourable opinion is naturally formed. Beyond these are the smells, 
approaching to stenches, arising from butyric, ropy, and even putrid fer- 
mentation. 

552. Flavour. — This of course is one of the most crucial tests to 
which bread can be put. It is probably the only one adopted by the 
vast majority of the bread eating public. Fortunately, the judgment 
based on flavour is almost invariably a sound one ; a bread which 
pleases the palate is usually one that is wholesome. Having made this 
statement, it may be well also to indicate one direction in which the 
palate test is untrustworthy ; many people are extremely fond of hot 
rolls for breakfast. These luxuries are not, however, to be indulged in 
by everyone, for hot bread is not easily digestible. The reason is a 
simple one, the soft nature of bread, while still warm, causes it to be 
formed into balls in the mouth, which are swallowed without the due 
admixture with saliva. 

When tasting bread, nothing having a strong flavour should have 
been eaten for some little time previously ; a small piece of the bread 
should be put in the mouth, masticated, and allowed to remain there a 
short time before being swallowed. The flavour should be sweet, and of 
course there must be an absence of sourness or any marked objectionable 
taste. The physical behaviour of the bread in the mouth is also of im- 
portance. The bread should not clog or assume a doughy consistency 
in the mouth ; neither, on the other hand, must it be dry or chippy. 
In addition to tasting the dry bread, a slice spread with butter may be 
eaten. It need not be said that in this test the butter must be unex- 
ceptionable. 

553. Colour and Thickness of the Crust. — The crust should 

be of a rich brownish yellow tint ; neither too light on the one hand, 
nor too dark on the other. So far as is consistent with adequate baking 
the crust should be as thin as possible. 

The act of baking changes the character of several of the constituents 
of the flour. Thus the albumin is coagulated, and thereby rendered 
insoluble. The starch is partly, at least, rendered soluble by the 
gelatinisation consequent on heating. The fatty matters of the flour 
are unchanged ; at times, however, bread is found to contain fat over 
and above that normally present in flour. In fancy bread, butter or 
milk is sometimes used in the dough ; small quantities of lard are also 
employed by some bakers in order to give a special silkiness to the 
fracture where two loaves of crumby bread are separated from each 



460 



CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 



other. The ash is not materially affected in quantity. The water, 
varies considerably. Subjoined are the results of some analyses collected 
by Konig and quoted by Blyth : 





Mini- 
mum. 


Mini- 
mum. 


Mean for 

Fine 

Bread. 


Mean for 
Coarse 
Bread. 


Water 


2 6'39 


47-90 


38-5I 


4I-02 


Nitrogenous substances 


4'8i 


8'6 9 


6-82 


6-23 


Fat 


O'lO 


I '00 


077 


0*22 


Sugar 


0-82 


4-47 


2'37 


2-13 


Carbo-hydrates (Starch, &c.) 


38-93 


62-98 


49 '97 


48-69 


Woody-fibre 


o*33 


0*90 


0-38 


0-62 


Ash 


0-84 


1-40 


1-18 


1-09 



554. Quantity of Water in Bread. — Much has been written 

on this question of the quantity of water in bread. Thus, in " Bread- 
Analysis, a practical treatise," Wanklyn and Cooper quote as an im- 
proved method of making good white bread, that 6 lbs. of fine flour 
should be taken to 2 1 lbs. ( = 1 quart) of water. This means that 46-6 
quarts of water are to be taken to each sack of flour ! Taking these as 
the standard proportions, they calculate and assert that " well-made 
bread should contain some 34 per cent, of water, and the bread-solids in 
well-made bread will thus amount to 66 per cent." They then point 
out that " the bread to be met with in the market contains sometimes 
40 per cent, of water, and even much more than 40 per cent." In the 
subsequent paragraph this is styled "the profitable commercial operation 
of making 60 lbs. of bread-solids do duty for 66 lbs. of bread-solids." 
Further on they state that they " have already called attention to the 
fraud on the public which is involved in the supply of bread surcharged 
with water." These are serious accusations which are thus preferred 
by Wanklyn and Cooper against the baking community : charges of this 
kind should never be made without the amplest and most trustworthy 
evidence being forthcoming in their support. 

Let us examine a moment the nature and value of the evidence ad- 
duced. The recipe on which Wanklyn and Cooper's calculation is based 
is quoted from an old book, date 1813. Now at that time the Corn 
Laws were in full operation, and, as is well known, bread had to be 
made from flour which now would scarcely be deemed fit for cattle food. 
Thanks to the magnificent wheats and flours at this time to be obtained 
in the British markets, a baker would find himself puzzled to discover a 
flour that could be worked with 46 quarts of water to the sack. Doubt- 
less the surcharging of bread with water is an offence against the 
community, but it is fortunately an offence that immediately brings 



BREAD ANALYSIS. 461 



with it its own punishment, inasmuch as the injury done to the appear- 
ance of the bread, by excess of water, diminishes its saleable value. 
Wanklyn and Cooper, in laying down their hard and fast line that no- 
more than 46 quarts of water to the sack should be used, take no 
cognizance of the fact that different flours vary most widely in the 
quantity of water they require to make a dough of the same stiffness. 
Thus among the number of flours examined by the author, he finds that 
to make a dough of standard consistency, some flours, principally those 
milled from weak English wheats, take 60 quarts of water to the sack ;, 
others take 70 and even 80, while one sample he has examined required 
98 quarts of water to produce a standard dough. With such wide 
divergencies among flours, how can a baker possibly adhere to the rigid 
rule of 46 quarts to the sack 1 Wanklyn and Cooper proceed to quote 
analyses made by them of samples of bread obtained from Peterborough : 
they find that 17 samples contained, on the average, 40 per cent, of 
water, that 11 contained 34 per cent., and that 14 were intermediate. 
Wanklyn and Cooper state that these Peterborough samples " exhibited 
an astonishing tendency to become mouldy," but say — "unfortunately 
we did not take the requisite precautions to ascertain by direct observa- 
tion whether or not the degree of mouldiness ran parallel with the 
degree of hydration." There is ample evidence that a high percentage 
of water does not necessarily produce a bread that rapidly develops 
mouldiness. It is well known that Vienna bread, and fancy bread 
generally, made from high class patent flours, contain much more than 
the average percentage of water : yet these are of all breads the least 
susceptible to mould. It is no uncommon thing to see a sample of such 
bread which has been preserved for years, and which nevertheless ex- 
hibited not the slightest trace of fungoid growth. 

The question may fairly be asked — On what principle is a decision 
to be made as to whether a bread contains too much water 1 In reply, 
the loaf, after having cooled say two hours after being removed from 
the oven, should on being cut feel just pleasantly moist, not dry and 
chippy, nor on the other hand, in the slightest degree sticky or clammy. 
A second loaf, on being examined in the same way when two days old, 
should answer to the same tests, and should not show the slighest signs 
of sourness or mustiness. Some loaves of bread containing even 40 per 
cent, of water would very well pass this examination ; while others 
which might contain much less water would nevertheless be damp and 
sodden, rapidly turning mouldy or sour. Notwithstanding that the lat- 
ter contained absolutely the less water, they would still be condemned 
as containing more than they ought ; while the former would be 
returned as coming within the limit. The quantity of water permissible 
in a bread must depend on the nature of the flour used ; the offence is 
not in using sufficient water to a strong flour, but in adding more to a 
weak flour than it can properly take. 

Another question arises, would it not be well for the public to insist 
on being supplied with bread made from such flours as normally require,, 
for their conversion into bread, a low proportion of water 1 Again, in 
reply, the strongest flours, that is, those which naturally absorb the 
most water, are made from the soundest, best matured, and highest. 



462 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

class wheats ; so that the baker who uses a strong flour also uses a high 
priced flour. But even in districts where very strong flours are habitu- 
.ally employed, the buying public suffers no injustice in the matter of the 
price paid for solid bread stuffs ; for if the flours used are such that 
the bread contains a high percentage of water, and its production is 
thereby cheapened, natural economic laws force down the price. It is 
well known that in those districts where strong flour is used, the price 
of the bread per quartern loaf is low. 

555. Analytic Estimations. — In an ordinary analysis of bread, 
where the object is not to test for adulteration, the following estimations 
may be made : water, ash, and acidity. A thin slice should be cut from 
the middle of the loaf, the crust cut off, and then the interior portion 
crumbled between the fingers ; the crumbs must be thoroughly mixed, 
and at once placed in a bottle. 

556. Moisture. — Weigh out 5 grams in a counterpoised dish and 
dry until the weight is constant. The dish may conveniently be left in 
the hot-water oven over night. 

557- Ash. — Weigh out 5 grams in a tared platinum dish ; ignite 
gently until only a white ash remains, and weigh. A properly burned 
ash should not exceed 5 per cent. Should there happen to be more 
than this quantity adulteration may be suspected. 

558. Acidity. — Add 200 c.c. of distilled water to 10 grams of the 
bread ; after a quarter of an hour, shake up, allow to subside, and filter 
through a dry filter. Titrate 100 c.c. of the filtrate with decinormal 
soda, using phenophthalien as an indicator. The acidity may be calcu- 
lated as lactic acid. 

559. Fat. — This may be estimated, if wished, in from 10 to 25 
grams of the bread. Weigh, dry in the hot- water oven, and extract the 
fat by means of ether or light petroleum spirit in either of the fat ex- 
traction apparatus previously described. The method is precisely the 
.same as for flours. 






f 1 



ADULTERATION. 463 



CHAPTER XXY1. 

ADULTERATION. 

560. Standard works on the subject.— In giving directions 

for both flour and bread analysis we have hitherto confined ourselves to 
such modes of testing as enable us to determine the quality and charac- 
ter of each, apart from any considerations as to the presence or absence 
of any foreign substances. This portion of our task will not, however, 
be complete until an outline has been given of the processes employed 
in the analysis of flour and bread for the purpose of detecting adultera- 
tion. This branch of chemistry applied to the arts of milling and bak- 
ing has received considerable attention, and several standard works of 
reference have been written on the subject ; among these may be 
mentioned those of Allen and Blyth, both of which represent the most 
recent and authoritative opinions of chemists on the problem. For 
several of the tests to be hereafter described the writer is indebted to 
these works, to which the student is referred for further and more de- 
tailed information. 

561. Information derived from Normal Analysis.— Some 

-of the tests already mentioned in the description of the normal analysis of 
flour and bread serve also as indications as to whether a sample is adul- 
terated. Thus the moisture, if unduly high, points to the fact that the 
wheat has probably been damped ; water added for other purposes than 
the sufficient softening of the bran to permit the grinding to be readily 
performed must be looked upon as an adulterant. It is a debated 
point whether even such addition of water as this is permissible ; cer- 
tainly there should not be enough to greatly affect the percentage of 
moisture in the dressed flour. 

The percentage of ash in the flour affords some guide as to whether 
the sample has been treated with mineral substances. A flour ash, 
when properly burned, should amount to less than 1 per cent. ; greater 
quantities than this are probably due to mineral adulteration. 

562. Impurities and Adulterants of Flour.— The following 

are some of the foreign substances that are at times found in flour: seeds 
of other plants, as corn-cockle and darnel; blighted and ergotised grains 
— these are to be viewed rather as impurities than adulterants, the 
latter term being confined to those bodies wilfully added for purposes of 
fraud. Among these latter are rye, rice-meal, potato starch, meal from 
leguminous plants, as peas and beans, and the following mineral bodies : 
alum, borax, chalk, carbonate of magnesia, and bone ash. 

The tests for many of these substances are in part microscopical; the 



464 CHEMISTRY OF WHEAT, FLOUR, AND BREAD. 

chapters containing directions for practical microscopic work, provide 
information and data as to the making of such tests. The following are 
the principal chemical tests for the bodies above mentioned : — 

563. Darnel.— Treat a little of the flour with alcohol (rectified 
spirits of wine, not methylated spirits), digest at 30° C. for an hour, 
shaking occasionally. Filter and examine the filtrate. This should be 
clear and colourless, or at most should be only of a light yellow colour. 
In event of the flour containing darnel the alcholic extract is of a 
greenish hue, and has an acrid and nauseous taste. 

Treatment with alcohol and a small quantity of acid is a useful test 
for other adulterants. Extract the flour with 70 per cent, alcohol (i.e., 
a mixture of alcohol and water, containing alcohol equivalent to 70 per 
cent, of absolute spirit), to which 5 per cent, of hydrochloric acid has 
been added. Pure wheat or rye flour yields a colourless extract ; barley 
or oats gives a full yellow tint ; pea-flour, orange-yellow, mildewed 
wheat, purple-red, and ergotised wheat a blood-red colouration. 

564 Ergot and Mould. — To test flour for ergot, exhaust 20 grams 
with concentrated alcohol in a fat extraction apparatus ; notice the 
colour, which in the presence of ergot is more or less red. Mix this 
solution with twice its volume of water, and shake up separate portions 
of this mixture with ether, amyl-alcohol, benzole, and chloroform. 
Ergot imparts a red colour to the whole of these solvents. 

Yogel recommends the flour should be stained with aniline violet, and 
then examined under the microscope : should any of the starch granules 
have been attacked by ergot or other fungoid growths they acquire an 
intense violet tint, while if they are perfectly sound they remain com- 
paratively colourless. 

Ergotised flours evolve the peculiar fish-like odour of trimethylamine 
when heated with a solution of potash : the same smell is, however,, 
evolved by flour otherwise damaged. The test is of service in dis- 
tinguishing between sound and unsound flours. 

The use of mouldy wheat for the manufacture of flour can readily be 
detected by placing the sample in a tightly stoppered bottle, damping it 
and placing it in a bath heated to about 30° C. Any mouldy taint can 
readily be detected after thus standing for two or three hours. 

SG5. Mineral Adulterants. — The presence or absence of most 
foreign mineral matters will have been indicated by the percentage of 
ash yielded. Alum is, however, added to flour in quantities too small to 
be thus detected. One of the most ready means of separating mineral 
substances from flour is by means of what is termed the 

566. Chloroform Test. — This test depends on the fact that chloro- 
form has a density higher than that of the normal constituents of flour, 
but lower than that of minerals generally ; consequently, on agitating a 
mixture of flour and chloroform, and then allowing it to rest, the flour 
rises to the surface, and any mineral adulterants sink to the bottom. 
On the small scale, for the purpose of a qualitative test, a large dry 
test-tube may be about one-third filled with the flour, then chloroform 
added to within one inch from the top. The tube must then be corked 
and violently shaken, after which it must be allowed to rest for some 



ADULTERATION. 465' 



hours ; the mineral matter will then be found to have sunk to the 
bottom. For quantitative purposes a glass " separator " is requisite. 
This is a cylindrical vessel some two inches in diameter, eight or ten. 
inches in length, stoppered at the top, and furnished with a stopcock at 
the bottom. Introduce in this vessel 100 grams of the flour, and 
about 250 c.c. of methylated chloroform ; treat as directed for the 
smaller quantity. When the separation is effected, open the stopcock 
and allow any sediment, with as little as possible of the liquid, to run 
through. Treat this again with a little more chloroform in a smaller 
separator, and once more drain the sediment off through the stopcock 
into a watchglass, or small evaporating basin. Allow the chloroform to 
evaporate ; treat the dry residue with a small quantity of water, and 
filter. Any plaster of Paris or other insoluble mineral matter will 
remain on the filter, and may be ignited and weighed. Evaporate the 
solution to dryness, and examine the residue carefully with a low power 
under the microscope for any crystals of alum. 

567. Special Test for Alum! — The most convenient test for 
alum in flour consists in adding thereto an alkaline solution of logwood. 
Take 5 grams of recently cut logwood chips and digest them in a closed 
bottle with 100 c.c. of methylated spirit. Also make a saturated solu- 
tion of ammonium carbonate. Mix 10 grams of the flour with 10 c.c. 
of water, then add 1 c.c. of the tincture of logwood and 1 c.c. of the 
ammonium carbonate solution, and thoroughly mix the whole. With 
pure flour the resultant mixture is of a slight pinkish tint. Alum 
changes the colour to lavender or full blue. The blue colour should 
remain, on the sample being heated in the hot-water oven for an hour 
or two. 

568. Alum in Bread. — Bread is tested for alum by first taking 
5 c.c. of the tincture of logwood, 5 c.c. of the ammonium carbonate 
solution, and diluting them down to 100 c.c. This mixture must at 
once be poured over about 10 grams of the crumbled bread in an eva- 
porating basin. It is allowed to stand for five minutes and then the 
superfluous liquid drained off. Slightly wash the bread and dry in the 
hot-water oven. Alum gives the bread treated in this manner a lavender 
or dark blue colour, which is intensified on drying. Pure bread first 
assumes a light red tint, which fades into a buff or light brown. After 
some practice this test gives satisfactory results, and is so sensitive that 
as little as 7 grains of alum to the four pound loaf have been detected. 
The depth of colour affords a means of roughly estimating the quantity 
of alum present. It is essential that the tincture of logwood be freshly 
prepared, and that the test be made immediately after mixing the 
tincture of logwood and ammonium carbonate solution. 



THE END. 







INDEX. 




A 




'AGE. 


PAGE. 


Absolute Temperature 




10 


Alcohol, Methyl .... 


37 


,, Weight of Hydrogen 




12 


Alcohols ..... 


36 


Acetic Acid 




41 


,, Propyl, Butyl, and Amyl 


39 


,, Ferment . 




213 


Alcoholic Fermentation, and Yeast 


98 


Acid, Acetic 




41 


Alcoholic Fermentation, Substances 




,, Butyric 




41 


inimical to . 


114 


,, Carbonic . 




26 


Alcoholic Fermentation, Substances 




,, Hydrochloric 




23 


produced by . 


121 


, , , , Use of, in Bread- 




Alcoholic Fermentation, Substances 




making . 




332 


susceptible of 


98 


.,, Lactic 




42 


Alcoholic Fermentation, Viewed as 




., Nitric 




29 


a chemical change 


98 


,, Nitrous 




29 


Aleurometer .... 


39i 


, , Phosphoric 




3 1 


Alkalies ..... 


13 


,, ,, Determination of 


403 


Alkaline Permanganate Solution . 


43 r 


,, Silicic 




3i 


Alkaloids ..... 


44 


,, Succinic 




43 


Alum, Copper Sulphate, and Lime, 




,, Sulphuric . 




30 


Use of .... 


325 


,, ,, Normal 




417 


Alum, Special Test for 


465 


,, Sulphurous 




30 


American Wheats, Composition of 


243 


,, Tartaric 




43 


Ammonia ..... 


28 


Acidimetry and Alkalimetry . 




416 


Ammonias, Compound 


44 


Acidity of Meals or Flours . 




+22 


Ammonium Salts 


28 


Acids, Bases, and Salts 




13 


,, Chloride, Standard 




,, Basicity of 




14 


Solution 


430 


,, Organic . 




41 


Amyl Alcohol .... 


39 


Adulteration 




4^3 


Analyses of English and Foreign 




Aeration of Bread, other thar 


l by 




Wheats .... 


237 


Yeast .... 




330 


Analysis of Bread 


555 


Aeration Process . 




333 


Analytic Apparatus 


367 


Albumin .... 


85, * 


,, Balance 


368 


» Egg 




86 


,, ,, Adjustment of . 


37i 


„ Insoluble, or Vegetable 




,, Weights 


3Ji 


Fibrin 




90 


Appert's Method of Preservation 




Albuminoids or Proteids 




85 


from Putrefaction . 


130 


,, Composition of 




85 


Artificial Drying of Wheats and 




,, Estimation of, by Am- 




Flours ..... 


288 


monia Process 




428 


Ascospores ..... 


113 


, , Estimation of, 


by' 




Ash of Wheat . . .56, 


236 


Combustion Process 


423 


,, Wheats and Flours, Deter- 




,, Insoluble, of Wheat, 




mination of . 


403 


Gluten 


8S, 


236 


Aspergillus Glaucus . 


214 


,, List of 


. 


85 


Atmosphere .... 


27 


,, Soluble 




94 


Atomic or Combining Weights 


4 


,, „ of Wheat 


88, 


2 35 


,, „ ,, List of 


2 


,, Total, Estimation 


of. 


43 & 


,, Theory .... 


5 


,, True, Estimation of . 


437 


Atomicity or Quantivalence . 


14 


Alcohol, Absolute 


. 


38 


Atoms and Molecules . 


5 


,, ,, Preparation of . 


452 


Attenuation .... 


199 


,, Detection of . 




38 


Automatic Temperature Regulator 


176 


Ethyl . 




37 


Avogadro's Law .... 


11 



468 



INDEX. 



B 




PAGE. 




PAGE. 


Bacilli , 




124 


Breadmaking, London , 


, • 307 


Bacillus Subtilis . 




124 


,, Manchester 


• 309 


Bacteria .... 




123 


,, Objects of 


• 307 


,, Diastasic Action of . 




126 


„ Scotch Practice 


• 30Q 


Bacterial Fermentation, Action oj 




Break Flours, Composition of . 261 


Oxygen on . 




129 


Bromine, Iodine, and Fluorine . 31 


Bacterium Lactis 




J 25 


Brown, Heron, and Morris 


' Re- 


„ Termo 


, 


123 


searches 


• 77 


Bailey-Baker Oven 




35« 


" Brownian " Movement 


. 124 


Bakehouses, Sanitary Aspects 


of ! 


322 


Bunt .... 


. 217 


Baker's Flour Sifter 


. 


345 


Burette, Strength 


250, 383 


,, Patent Oven Light . 




365 


Burettes and Floats 


• 375 


Baking .... 


. 


3 J 9 


Butyl Alcohol 


• 39 


Baking Machinery and Appliances ; 




Butyric Acid 


. 41 


Sanitary, Working, and 


Fi- 




, , Fermentation . 


. 129 


nancial Aspects of . 




342 






Baking Powders 




33o 


c 




,, Tests 




400 






Balance, Analytical 




368 


Calcium and its Compounds 


. 32 


Barley, Composition of 




233 


Calculations of Quantities 


• 17 


,, Meal, Unsuitability of 


for 




Camera Lucid a . 


• 5i 


Breadmaking . 


. 


336 


Cane Sugar 


66, 73 


Barm, Parisian . . . 


. 


203 


,, Estimation of 


• 439 


„ Virgin 




202 


,, Hydrolysis of 


80,84 


Barms, Scotch Flour . 




201 


Carbohydrate, Definition of 


. 59 


,, ,, Thorn's Formulae 


202 


Carbohydrates, Estimation of . 438 


Base, Definition of 


, 


13 


,, Transformation of . 75 


Basicity of Acids 


. 


H 


Carbon 


. 24 


Beard of Wheat . 




226 


,, Dioxide . . . 


• 25 


Birmingham Methods of Bread- 




,, Monoxide. 


. 25 


making . . 




308 


Carbonates 


. 26 


Bleaching Powder, Chloride of 




Casein 


• 85 


Lime .... 




24 


,, Vegetable, or Legum 


n . 87 


Blending of Flour 




336 


Cellulose . . 59, 68, 22^ 


„ of Wheat 


295 


336 


,, Estimation of . 


• 544 


Blood Albumin . 




87 


,, of Bran . 


. 229 


Boyle's Law 


. 




,, of Endosperm 


. 231 


Bran ..... 


223 


, 226 


of Wheat 


• 234 


„ Cellulose 


, 


229 


Cerealin 


76, 9 J 


,, Composition of 




263 


,, Cells 


, 225 


Bread, Aerated . 




333 


Cereals, Composition of 


• 233 


,, Analysis . 


457 


462 


,, Diseases of 


. 215 


,, Colour 




457 


Chemical Calculations . 


. m 


,, Composition of . 


. 


460 


,, Combination by Volume 12 


,, Cooling of 




321 


byW 


eight 3 


,, Flavour 




459 


,, Composition of Wheat . 233. 


,, Gluten 




334 


,, Equations 


. 4 


,, Leavened . 




328 


,, Laboratory . 


• 367 


,, Musty and Mouldy . 




215 


Chemistry, Definition of 




,, Odour . 




459 


Chicandard on Panary Fermenta- 


,, Pile . . _ . 


. 


458 


tion 


. 329 


, , Quantity of Water in 




460 


Chloride of Lime, Bleaching 


Pow- 


,, Relative Nutritive values of 


der 


. 24 


different varieties of 


. 


335 


Chlorides 


. 24 


,, Souring of 




321 


Chlorine 


• 23 


,, Test for Alum in 




465 


Chloroform . 


. 40 


,, Texture 




458 


,, Test on Flour 


• 464 


,, Vienna 




327 


Chlorophyll 


. IOI 


,, Whole Meal 




332 


Cilium 


. 123 


Breadmaking 




305 


Colloids 


. 20 


,, Birmingham Practice 


308 


Colour of Bread . 


• 457 



INDEX. 



469 



PAGE. 

Colour of Flour .... 245 
„ Scale for Flour . . . 246 
Combining or Atomic Weights . 4 
Combining or Atomic Weights, 

List of .... 2 

Combining Proportion . . 4 

Combustion and Ammonia Pro- 
cesses, Comparison between . 436 
Combustion Furnace . . . 424 
,, Tubes, Iron . . 424 

,, Process for Estimation 

of Albuminoids . 423 
Commercial Testing and Chemical 
Analysis of Wheats and 
Flours . . . 367, 378 
Commercial Testing and Chemical 
Analysis of Wheats and Flours, 
Importance of 378 
Commercial Testing and Chemical 
Analysis of Wheats and Flours, 
Practicability of . . . 379 
Commercial Testing and Chemical 
Analysis of Wheats and Flours, 
Principles of 378 
Composition of Roller Milling Pro- 
ducts 257 

Compound Ammonias . . -44 
,, Definition of .2 

,, Radicals . . .13 

Conidia 102 

Constitutional Formulae . • 4 
Cooling of Bread . . . .321 
Copper Sulphate, Employment of, 

in Breadmaking . . . 325 
Counterpoised and Weighed Filters 407 
Crystalloids and Colloids . . 20 
Cuticle of Wheat Grain . . 224 



Damping Wheats . . . 280 

Darnel ..... 464 

Dauglish's Process of Aerating 

Bread . . . . .333 
Decinormal Solutions . . .418 
Desiccator ..... 397 
Detection of Alcohol . . .38 
Dextrin . . . 65, 73 

,, and Maltose, Polarimetric 

Estimation of . . 450 

,, and Sugar of Wheat . . 234 
,, Estimation of . . . 443 
,, Hydrolysis of . .81 

,, Molecular Constitution of . 79 
Dextrose or Dextro-glucose . . 67 
Diagram of Strength Results . 256 

,, of Results of Flour Analy- 
ses . . . 277 
,, of Roller Milling Products 264 
Dialysis . . . . 19 
Diastase .... 76, 92 



Diastase, Preparation of 

Diastasic Action of Bacteria 
,, or Diastasis 

Diastasis, Conditions and Sub- 
stances inimical to 

Diffusion, Gaseous 

Disease Ferments 

Diseases of Cereals 

Dough, Killing or Felling of 

Doughing Machine, Drum . 
,, ,, Melvin's 

,, ,, Pfleiderer's 

,, ,, Thomson 

,, Machines 
,, ,, Cleaning 

Drum Kneading Machine 

Drying Wheats and Flours . 



• 453 
. 126 

. 76 

82,84 
19 
131 

215 
358 
35^ 
355 
349 
353 
349 
358 
356 
288 



Egg Albumin ... . .86 
Element, Definition of . . 2 

Elements, List of ... 2 

Empirical Formula . . 17 

Endocarp 224 

Endosperm ..... 223 
,, Cellulose of . .231 

English and Scotch Wheats, Ana- 
lyses of .... 238 
Epicarp ..... 224 
Epidermis of Wheat Grain . . 224 
Episperm ..... 225 
Equations, Chemical ... 4 
Erdmann's Float .... 376 
Ergot . . . - . 218, 464 
Ethereal Salts . . . .40 

Ethers 40 

Ethyl 35 

Ethyl Alcohol . . . -37 
Expansion and Contraction of Gases 10 



Fat, Determination of , . . 408 
Fats and Soaps . . - 42 

Fatty Acids, or Acids of Acetic 

Series . . . -.41 
Fatty Matters of Wheat . 57, 234 
Fehling's Solution . . . 438 

Ferment, Potato . . . 3 12 

,, Treating Machinery . 343 
Fermentation . . . - 95 



Fermentation 



Alcoholic [see also 
under Alcoholic 
Fermentation) . 98 
Butyric . .129 

Definition of . .96 
Earlier Views on . 95 
Effect of Quantity of 

Yeast on . .168 
Effect of Salt on . 158 



470 



INDEX. 



Fermentation, Effect of Tempera- 
ture on . . 163 
,, Experimental Basis 

of Modern Theory of 97 
,, Lactic . .123, 125 

,. Loss during . .318 

Modern Theory of . 97 
. , of Filtered Flour In- 

fusion . . 145, 152 
of Flour, Effect of 
Salt on . . 156 
, , Origin of Term . 95 

,, Panary, Chicandard 

on 329 

,, Panary, Mege-Mou- 

ries on . . 328 

,, Panary, Review of . 311 

,, Panary, Theories of 328 

,, Pasteur's View of . 96 

,, Putrefactive . .129 

„ Spontaneous . 131, 192 

y , SubstancesinimicaltoU4 

,, Varieties of . .98 

,, Viscous . . .128 

Fermentative Properties of Various 

Substances — 

Albumin . . . . .140 

Filtered Flour Infusion . 145, 152 

Flour . . .158, 147, 172 

Pepsin 140 

Potato and Potato Infusion . 158 
Separate Constituents of Flour . 147 
Starch . . . . 147, 158 
Sugar . . . 140, 162, 172 

Wort 145 

Yeast Mixture . . 140, 145, 158 

Fibrin 85 

Filter Ash, Weight of . . . 407 
Filters, Counterpoised and Weighed 407 

Flagellum 123 

Flasks, Measuring . . . 377 

,, Pasteur's . . . .116 

Float for Burette . . . 376 

Flour Analyses, Results of . . 296 

,, Barm Recipes, Suggested 

Modifications of . . 206 
,, Barms .... 201 

,, ,, Thorns' Formula . 202 
,, ,, "Glasgow Baker's" 

Formula . . 203 
„ Blending . . . .336 
,, Colour of . . . 245, 290 
,, Composition of . . . 262 
,, Effect of Germ on , .291 
,, Impurities and Adulterants of 463 
,, Self-Raising . . . 332 

,, Sifting Machines . . 344 

,, Stability of . . .315 

„ Testing . . 390 

,, Strength of . 248, 290, 383 

,, Sugar in ... 152 



Flour Testing 


PAGE. 
• .383 


,, „ with Viscometer . 386 


Flours, Artificial Drying of 


. 288 


,, Produced during Gradual 


Reduction 


275. 338 


Fluff .... 


. 263 


Fluorine 


• 31 


Foreign Wheats, Composition of . 241 


Formula from percentage Composi- 


tion, Calculation of 


. 16 


Formulas 


3 


,, Constitutional 


• 4 


,, Empirical 


• 17 


Fruit 


. 312 


Fungi 


. IOI 


Fusel, or Fousel, Oil . 


. 40 


G 




Gas Ovens .... 


• 364 


Gaseous Diffusion 


. 19 


Gelatinisation of Starch 


. 70 


Germ, Composition of 


. 263 


,, Effect of on Flour 


. 291 


,, Structure of 


. 222 


Glazing .... 


. 3 2 ° 


Glucose, or Grape Sugar 


. 67 



Gluten . . SS t 94, 236, 290 

,, Bread . . . .334 

„ Cells .... 220 

,, Composition of . . .88 
,, Fermentation of . .147 

,, Non-existence of, as such in 

Flour . . . -9° 

„ Results, Interpretation of . 397 

; , Testing . . . .391 

,, „ The Aleurometer . 391 

Glutin, Gliadin, or Vegetable 

Gelatin . . 85, 89 
, , Mucin, and Vegetable Fibrin, 

Mutual Relations of . 90 

Glycerin 40 

Gradual Reduction, Flours pro- 
duced during . . 275, 338 



H 



Heat Measurements 


8 


,, Solid and Flash . 


320 


High Yeast . 


102 


Higher Fatty Acids, and Salts of . 


42 


Hilum , 


225 


Homologues, Definition of . 


43 


Hot Water Oven 


39 6 


Hydrides of Organic Radicals, 




Paraffins . 


36 


Hydrochloric Acid 


23 


,, ,, Use of in Bread- 




making 


332 
21 


jnyurugcii • • • • • 
,, Absolute Weight of 


12 



INDEX. 



471 



Hydrolysis . 

,, Details of 
Hydrolytic Agents 
Hyphse , 



7 J 
80 

75 
102 



I 

Important Temperatures . .10 
Indicators, Litmus and Phenol- 

phthalien . . . .417 
Insoluble Albumin, or Vegetable 

Fibrin . . . QO 

„ Albuminoids of Wheat . 88 

Invertin 75 

Iodine 31 

,, Reaction with Starch . . 64 

Iodoform 41 

Iron Combustion Tubes . . 424 
Isomerism . . . . 43 

K 

Killing or Felling of Dough . 358 

Kneading Machines . . . 349 



367 

125 

125 

. 67 

. 328 
85,87 

• 325 
417 
307 
325 



Laboratory . 

Lactic Acid . . .42 

,, Fermentation . .123 
Lcevulose, or Lsevo-Glucose 
Leavened Bread . 
Legumin 

Lime, Use of, in Breadmaking 
Litmus .... 

London Methods of Breadmaking 
Low Grade Flours, Working with 

M 

Magnesia Mixture . . . 404 

Magnification in Diameters . . 50 
Maize, Composition of . . . 233 
Malt, Aqueous Extract of . .73 
,, Saccharification of during 

Mashing. . . 81, 84 

,, Extract, Action of on 

Bruised Starch . . 77 
,, Extract, Action of on Cane 

Sugar ._ . . .77 
„ Extract, Action of on Starch 

Paste .... 78 
,, Extract, Action of on Un- 

gelatinised Starch . . 77 
Malto-Dextrin . . . .68 

Maltose 66 

,, Estimation of, by Fehling's 

Solution . . . 442 

,, Hydrolysis of . . .81 
,, Molecular Constitution of . 79 
Maltose, Polarimetric Determination 

of .... 450 



Manchester Methods of Bread 

making 
Mashing Malt together with Un 

malted Grain 
Mason Continuous Baking Oven 
Matter, Indestructible . 
Measures of Weight and Volume 
Mege-Mouries on Panary Fer- 
mentation 
Melvin's Kneading Machine 
Metalloids or Non-metals 
Metals 
Metamerism 
Methyl 

,, Alcohol 
Methylated Spirits of Wine 
Metric System 
Micrococcus Prodigiosus 
Micromillimetre, mkm. 
Microscope, Description of 

,, How to Use 

Microscopic Character of Starches 61, 69 

„ Objects, Measurement 

of . 

, , Sketching and Tracing 

Middlings and Semolinas 
Mildew 
Milk Sugar 
Mixture, Definition of . 

Mkm 

Modern Baking Machinery and 

Appliances . 
Moisture, Estimation of 
,, of Flour 

of Wheat 
Molecular Constitution of Starch, 

Dextrin, and Maltose . . 79 

Molecules 5 

Molybdic Solution . . . 403 

Mould 464 

Moulds and Fungoid Growths . 213 
Mucin or Mucedin . . 85, 90 
Mucor Mucedo . . .102,214 
Musty and Mouldy Bread . .215 
Mycelium ..... 102 
Mycoderma Aceti . . .213 

,, Vini . . 120, 196 

Myosin, Vegetable . . .91 



N 



Nessler's Solution . . . 429 
Nicol's Prisms . . . -53 

Nitrates 29 

Nitric Acid 29 

Nitrogen . . . . .27 
Nitrogenous Organic Compounds . 44 
Nitrous Acid and Nitrites . . 29 
Normal Sodium Hydrate . . 418 
,, ,, Carbonate . . 416 



3°9 

82 

36i 

2 

6 

328 

355 

3 

3 

44 

35 

37 

39 

7 

214 

50 

46 

48 



49 

5i 
261 
216 

67 
2 

50 

342 
398 
290 
236 



472 


INDEX. 




PAGE. 




PAGE 


Normal Solutions 


416 


Phosphorus, Phosphoric Acid, anc 




,, Sulphuric Acid 


417 


Phosphates .... 


31 


,, Temperature and Pressure 


II 


Physical Structure of Wheat Grain 


219 


N. T. P. . . . . . 


1 1 


Pile of Bread ... 


458 


Nutritive Values of different Varie- 




Pipettes . . . 


377 


ties of Bread 


335 


Polarimeter, The 


445 






Polarimetric Estimations 


444 


o 




Polarisation of Light . 


52 






Polymerism 


43 


Oats, Composition of . 


233 


Potato Ferment .... 


312 


Offals, Composition of . 


202 


Potatoes, Action of, on Fermenta 




Organic Acids .... 


41 


tion . . . .158 


, 162 


,, Chemistry, Definition of . 


34 


Potash, Determination of . 403 


, 407 


,, Compounds 


34 


Potassium and its Compounds 


32 


,, ,, Classification of 


35 


Precipitates, Washing and Ignitior 


1 


,, ,, Composition of 


35 


of . . . . 


405 


,, ,, Nitrogenous 


44 


Proof Spirit . . 


38 


,, Radicals 


35 


Propyl Alcohol 


39 


,, ,, Hydrides of, 




Proteids or Albuminoids , . 


85 


Paraffins , 


36 


,, Composition of 


85 


Organised Structures . 


34 


,, List of . 


85 


Osmose and Dialysis . 


19 


Ptyalin .... 


75 


Oven, Bailey-Baker 


358 


Putrefaction and its Relation to 


,, Light, Baker's Patent 


365 


Diastasis 


. 92 


., Mason, Continuous Baking 


361 


,, Conditions inimical 


,, Perkin's Steam . 


362 


to 


130 


,, Thompson's Gas 


3 6 4 


,, Products of 


• 131 


Ovens ...... 


358 


Putrefactive Fermentation, Actior 


1 


,, Author's Personal Opinions 




of Oxygen on 


. 129 


on ... 


366 


Putrefactive Fermentation or Putre 




Oxides of Nitrogen 


29 


faction .... 


129 


Oxygen 


21 






Ozone ..... 


22 


Q 




P 




Quantities, Calculation of . 


• 17 






Quantity of Heat 


10 


Panary Fermentation, or Panifica- 




Quantivalence of Atomicity . 


. 14 


tion, Chicandard on 


329 






Panary Fermentation, Mege 




R 




Mouries on . 


328 






Panary Fermentation, Review 




Radicals, Compound . 


• 13 


of. . 311 


313 


,, Organic 


35 


Panary Fermentation, Theories of 


328 


Remedies for Sour Bread 


324 


Paraffins, Hydrides of Organic 




Rice, Composition of . 


• 233 


Radicals . 


36 


Roller Milling Products, Com 




Parisian Barm . . . . 


203 


position of . 


257 


Pasteur's Flasks .... 


116 


Roller Milling Products, Diagran 


1 


„ Fluid .... 


140 


of .... 


. 264 


Patent Yeast .... 


191 


Roller Milling Products, Richard 




,, Recipes 


197 


son's Analyses of . 


266 


Pekar's Test for Flour . 


245 


Ropiness in Beer and Bread . 


128 


Penicillium Glaucum . .102 


213 


Rousing, Action of, on Yeast 109 


, 197 


Pepsin and Peptones . 


44 


Rye, Composition of . 


233 


Percentage Composition from For- 








mula, Calculation of 


15 


s 




Perkin's Steam Oven . . 


362 






Petroleum Spirit, Rectification of. 


408 


Saccharification . 


76 


Pfleiderer's Doughing Machine 


349 


„ of Malt during 




,, Flour Sifter 


348 


Mashing . 


81 


Phenolphthalien .... 


417 


Saccharomyces Albicans 


121 


Phosphoric Acid, Determination of 


403 


,, Cerevisce 


102 



INDEX. 



473 





PAGE. 




?AGE. 


Saccharomyces Cerevisce, Life His- 




Starch, Preparation and Manufac- 




tory of . . 


I03 


ture of . 


64 


,, Ellipsoideus . 102 


119 


„ Properties of, in Solution . 


63 


„ Minor . . 102 


Il8 


,, Saccharification of 


76 


,, Mycoderma,ox My- 




„ Solubility of 


62 


coderma Vint 


I20 


,. Solution, Reactions of 


72 


,, Pastorianus 102 


119 


Starches, Microscopic Character ol 




Salt, Definition of 


l 3 


Various .... 


61 


,, Common, Action of on Fer- 




, , Microscopic examination < 


3f69 


mentation 156, 158, 305 


318 


Steam Oven .... 


362 


Sanitary Aspects of Bakehouses . 


322 


Strength Burette . . . 250, 


383 


„ ,, Baking Ma- 




,, Determinations by Visco- 




chinery . 


342 


meter 


252 


Schizomycetes .... 


123 


„ of Flour . . 248, 383 


,, Spore Formation of . 


124 


,, of Flour Results, Diagram 


Scotch Flour Barms 


201 


of ... 


256 


,, Methods of Breadmaking . 


309 


,, of Yeast 


133 


.Section Cutting and Mounting 


221 


,, of Yeasts 


207 


Self-Raising Flour 


332 


Substitution, or Compound, Am- 




Semolinas and Middlings 


26l 


monias .... 


44 


Sharps, Composition of 


262 


Succinic Acid .... 


43 


Silicon, Silica, and the Silicates . 


31 


Sugar and Dextrin of Wheat 


234 


Sifting Machines for Flour . 


344 


,, • Cane, Inverted, Polarimetric 




Smut 


216 


behaviour of . 


449 


,, Identity of with Yeast 


217 


,, Polarimetric estimation of . 


449 


Soaps and Fats .... 


42 


Sugars 


66 


Soda-Lime ..... 


423 


,, Estimation of . 


438 


Sodium Chloride .... 


305 


„ by Fehling's 




,, Compounds 


33 


Solution . 


439 


Solid and Flash Heats 


320 


Sulphur ..... 


29 


Soluble Albuminoids . 


94 


,, Dioxide . . . . 


30 


„ „ of Wheat 88, 


235 


Sulphuretted Hydrogen 


29 


,, Extract . . . 420, 


421 


Sulphuric Acid and Sulphates 


30 


,, ,, of Wheat 


235 


Sulphurous Acid and Sulphites 


30 


Sour Bread, Remedies for 


324 


Symbols ..... 


3 


Souring of Bread .... 


321 


T 




Soxhlett's Extraction Apparatus . 


409 




Special Methods of Breadmaking . 


327 


Tailings, Composition of 


260 


Specific Gravity of Worts and 




Tartaric Acid .... 


43 


Attenuation .... 


199 


Temperature .... 


8 


Spirits of Wine . . . . 


38 


,, Absolute Zero of 


10 


„ Methylated . 


39 


,, Automatic Regulator 


176 


Sponge Stirrers .... 


349 


,, Effect of, on Fermen- 




Sponging and Doughing . 315, 


317 


tation . 


163 


Spontaneous Fermentation . 


131 


Testing with Viscometer 


386 


Sporangia ..... 


102 


Thermometer .... 


9 


Spores 


102 


Thermometric Scales . 


9 


Sporular Reproduction of Yeast, 




Thompson's Gas Oven 


364 


Thorns on . 


112 


Thorns' Doughing Test and Table 


249 


Stability of Flour 


315 


Thomson Kneading Machine 


353 


„ . Tests . . •. 


39o 


Total Albuminoids, Estimation of 


436 


Starch ..... 


60 


True Albuminoids, Estimation of . 


437 


„ Action of Caustic Alkalies 




u 




and Zinc Chloride on 63, 72 




,, Action of Diastase on 


76 


Unsound, or very low grade Flours, 




,, Estimation of 


45i 


Working with 


325 


,, Fermentation of 


H7 


U-tube 


424 


,, Gelatinisation of 


70 


V 




„ Hydrolysis of 76, JJ, 78, 80, 82 




,, Molecular Constitution of . 


79 


Vegetable Albumin . 


87 


,, of Wheat .... 


234 


,, Casein, or Legumin 


^7 



474 



INDEX. 



Vegetable Myosin . . .91 

Vernier, Description of . . 448 
Vibrio Subtilis . . . .124 
Vienna Bread .... 327 
Virgin Barm .... 202 

Viscometer 250 

,, Mode of Testing with . 386 

Viscometric Strength Determina- 
tions, Outline of Method . 252 
Viscometric Strength Determina- 
tions, Results of . . . 253 
Viscous Fermentation . . .128 

w 

Wanklyn and Cooper on Quantity 

of Water in Bread . . 460 

Water . . . .22, 305 

Bath 421 

Estimation of . 398 

free from Ammonia . . 430 
free from Carbon Dioxide . 418 
of Wheat . . . .236 
Solvent power of . 23 

Weighed Filters .... 407 
Weighing, Operation of . . 373 
"Weights, Analytic . . . 371 

Wheat, Blending . . . 295, 336 
Chemical Composition of . 233 
Commercial Assay of .381 

Constituents of • • 55 

Distribution of Gluten in . 295 
Fatty Matters of .57 

Grain, Construction of 55, 219 
Grinding of Samples . . 382 
Insoluble Albuminoids of, 

Gluten ... 88 

Mineral Constituents of . 56 

Soluble Albuminoids of . 88 

Weight per Bushel . .381 

,, ,, 100 grains . 382 

Wheats, Analyses of . 237 

,, Artificial drying of . . 288 

,, Damping of . . . 280 

Whole Meal Bread . . . 332 



Yeast 



and its Impurities 
as an Organism . 
Ascospores of . 
Bakers' Home made . 
Behaviour of Free Oxygen to 108 



Botanic Position of 

Brewers' . 

Brewing, Suggestions on 



98 
186 
101 

"3 

[90 



101 
187 
198 



Yeast, Budding of . . .103 
Chemical Composition of . 99 
Effect of Rousing on . 109 

Endogenous Division of .113 
Growth, Influence of Tem- 
perature on . . . 105 
High . . . .102 

High and Low, Converti- 
bility of . . .115 
High and Low, Distinctions 

between . . .115 

Identity of, with Smut . 217 
Insufficiency of either Sugar 
or Nitrogenous Matter 
only for Nutriment of .108 
Keeping Properties of .181 
Low or Sedimentary . 115 

Mal-nutrition of . .no 
Manufacture of . . .182 
Manufacture of Bakers' 
" Patent" or Home-made 
Malt and Hop . .191 
Manufacture of Brewers' . 182 
Manufacture of Compressed 187 
Manufacture of Scotch 

Flour Barm . . .201 
Methods for Isolation of, 

and other Organisms . T17 
Microscopic Study of 12 1, 184 
Mineral Matters necessary 

for Growth of . .107 

Mixture . . . 140, 180- 
Necessity of Saccharine 

Matter . . . .106 
Nitrogenous Nutriment . 107 
Pasteur's New High . .118 
Patent, Recipes . .197 

Purification of . . .126 
Reproduction of, other than 

by Budding . . .ill 
Strength Curves and Dia- 
grams . . . .143 
Strength of . _ . .133 
Substances requisite for 

Nutriment of . . 105 

Testing . 136, 179, 181 

,, Apparatus . 136, 176 
Thorns on Sporular repro- 
duction of . . .112 
,, Variety and Quantity used 316 
Yeasts, Strength of 207 



Zoogloea 123 

Zymase . . . . • 75 



ADVERTISEMENTS. Xlll 



SIIMZOILT'S 

ROLLER MILL SYSTEM. 



Durability of Machinery fully Guaranteed, 

Any parts shewing undue wear being exchanged free of cost. 



A Large number of the ROLLER 
MILLS put into the very first plants 
ordered from H. SIMON in 1879 are 
still at work without refluting or re- 
grinding of rolls. 



The expense in Repairs on these oldest 
ROLLER MILLS has been remark- 
able for its insignificance. 

First-class References with regard to this point. 



H. S I M N, 20, Mount Street, Manchester. 



XIV. ADVERTISEMENTS. 



SIMON'S ROLLER MILL SYSTEM, 



Patent REFORM PURIFIER 



This is the only Purifier that delivers automatically 
and separately, besides the ordinary tail, an inter- 
mediate quality of impurities, which in any other 
Purifier goes along with the Purified Middlings or 
Semolina, and deteriorates their quality. 

It is the early withdrawing of this intermediate 
quality of Offals which accounts for the astonishing 
and superior results of the " Reform " Purifier. 

No other Machine in the market even attempts this. 
The endless travelling Filter in the Reform is merely taking 
the place of a Dust Collector, which may as well be placed 
outside the Machine, and which is of no great influence on 
the work of the Purifier itself. 

Millers are invited to inspect the Reform, which is now 
at work in a considerable number of towns in England, 
Ireland, and Scotland, in many cases side by side with the 
best-known and other systems of Sieve Purifier. 



Samples of the work will be sent on application. 



H. SIMON, 

20, Mount Street, MANCHESTER. 



ADVERTISEMENTS. 



XV. 



" Parva scintilla excitavit magnum incendum." 



Fire Insurance 



Before building or making alterations for NEW 
MACHINERY, Millers are recommended to submit 
their Plans to, or consult with, 

John Henry Chatterton, 

Secretary, 

National Association of British and Irish Millers, 

And INSURANCE BROKER, 

61, Mark Lane, London, E. C, 

who will advise them on all points connected with the 
arrangement of their Buildings and Machinery, in order 
to meet the requirements of the Insurance Tariffs. 



Insurances effected with the following Companies :■ 



Atlas, 
Caledonian, 
City of London, 
Commercial Union, 
County, 
Equitable, 
Essex and Suffolk, 
Glasgow and London, 
Kent, 

Lancashire, 
Lion, 

Liverpool, London, and Globe, 
and with 



London and Lancashire, 

London and Provincial, 

Manchester, 

National, 

Northern, 

North British & Mercantile, 

Norwich Union, 

Royal, 

Scottish Provincial, 

South British, National and 

Westminster, [Adelaide, 

Yorkshire, 

Lloyd's. 



XVI. 



ADVERTISEMENTS. 



Zhc (Serm 
MILLING CO. 

Having acquired Mr. 
Thos. Muir's Patents 
for Degerming Grain 
intimate that they 
are prepared to grant 
licenses to 

Millers, Brewers, 

and Distillers 

throughout 

the Kingdom. 



DEGERMIM 
WHEATS MAIZE 

Applications to 

Mr THOMAS MUIR 

PATENTEE & MANAGER, 

Tradeston Mills, GLASGOW. 



05 
Fh CD 

si* 

V2 P 



w t3 

rrt CO 



bn 



CD ^ CO 

111 

.Cn 

^"8 | 

cu s: s 
^ *S £ 

M © 









<3 > 



To Millers, Farmers, Engineers, &. other owners of Steam-Power. 

DUNCAlfWAfsON 

NON-GUMMING 

OLIVOLIN 



& C0.'S 
E. 



It is a perfect En- 
gine & Machinery 
Oil. 
GRADE "A." 



GRADE "B." 




No charge for 

Casks. Free trials 

allowed. 

From 2s. lid. 

per gallon 

delivered. 

From 2s. 9d. per 

gallon delivered. 



LUBRICATING OILS OF EVERY DESCRIPTION, 

From Is. 6d. per Gallon upwards. 
HUNDREDS OF TESTIMONIALS RECEIVED. 

Full particulars on application to Duncan, Watson, & Co., Lubricating Oil 
and Grease Merchants and Manufacturers, Dashwood House, New Broad 
Street, London, E.C. 

AGENTS wanted in districts unrepresented. 

MILLSTONE BUILDER, WIRE WEAVER, 

MACHINE MANUFACTURER, 



General MILL FUKNISHEK. 




MILLSTONE MILLS for grinding 
Samples of Wheat for analysis- 
Illustration represents Ross' Patent 
Conical MilL 



SOLE MANUFACTURER- 



B. CORCORAN, 31, Mark Lane, London, E.O. 



ADVERTISEMENTS. 



THE 



ffcti^h & <f 0i*ip (&mitttintt 

BAKER ^NE> RESTAURATEUR. 

THE ONLY TRADE JOURNAL FOR 

CONFECTIONERS, PASTRY COOKS, BAKERS, RESTAURATEURS, &c. 

PUBLISHED ON THE 1st OF EVERY MONTH AT 

!, STRAND, LONDON, W.C. 



The British and Foreign Confectioner, Baker, and Restaur- 
ateur, is yearly developing its utility, and in order to render the 
journal absolutely essential as a Trade Organ, all Improvements, In- 
ventions, Novelties, &c., of the trade are brought under notice. Every 
effort is made to render the paper thoroughly complete and worthy of 
the important trade industry it represents. 



SUBSCRIPTION. 

Home ... ... ... ... 6s. per annum, post free. 

Foreign 7s. „ 

Single Copies and Back Numbers, post free, 8d. each. 

Post Office Orders, Postal Notes, or Cheques, to be made payable to Walter 
Williams. Penny Stamps taken in payment. 3» 

Subscriptions may commence with any month. The Volume commences with 
the May issue. Bound Volumes are not kept on Sale. 

Back Numbers. — Notice to Foreign Subscribers. — By the Post Office Regula- 
tions, the postage for abroad of all numbers over seven days old is sixpence per 
copy ; therefore, any one from abroad wishing for back numbers must add this 
rate of postage to the amount of subscription above mentioned. 

Most of the back numbers are still in print. 

Write to MANAGER, 

BRITISH AND FOREIGN CONFECTIONER, 

182, STRAND, 

LONDON, W.C. 



XV111. 



ADVEETISEMENTS. 



C/3 O 

e4> *■* 



* S a 


(/3 V3 




5 £ 


* "a 


<U 1) 


■S3 
n 2 


tuOO 




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<d i— i 


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£ h 


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15 

§ 

o 






s $ 

"- 1 V. 



U4 § 
CO 

CO 




ADVERTISEMENTS. 



XIX. 




HIGHEST AWARDS 
WHEREVER EXHIBITED, 



ESTABLISHED 1849. 




T. & T. VICARS, 

PATENTEES AND MANUFACTURERS OF 

BISCUIT AND BREAD 

^ /Ifoacbinen?, <& 

TRAVELLING OVENS, 

BAKERS' OVENS AND UTENSILS, 
FACTORIES PLANNED AND FITTED. 



MECHANICAL STOKEES FOE STEAM BOILEES, 
CHAE KILNS, OE SPECIAL PUEPOSES. 



Special attention is called to the jollowing recent Patents — 

Patent Biscuit Brake. 
Patent Biscuit Cutting Machine. 
Patent Biscuit Dough Mixer. 
Patent Bread Dough Mixer. 
Patent Drop Goods Machine. 



Patent Damping or Washover 
Machines for Biscuit Bakers, &c. 

Patent Self-Stoking Smokeless Fur- 
naces for Steam Boilers> Char 
Kilns, or special purposes. 



Prices and particulars on application to HEAD OFFICE, 

SEEL STIREET, LIVERPOOL 
ENGLAND. 



LIVERPOOL TELEPHONE 874 
EARLESTOWN 



TELEGRAPHIC {CUTTERS, LIVERPOOL. 



14, ST. HELENS. \ ADDRESSES, {VICARS, EARLESTOWN. 



XX. ADVERTISEMENTS. 



JOSEPH BAKER & SONS, 

Engineers anb patentees, 

58, CITY ROAD, LONDON, e.g. 

Works : Bell Yard, Featherstone St., Graven St, E.G. 



HIGHEST AWARDS EVER GIVEN FOR 

BAKING MACHINERY AND OVENS. 

INTERNATIONAL 

HEALTH 
EXHIBITION, 

Xon&on, 1884- 
ONLY GOLD MEDAL 

FOR 

BAKING MACHINERY AND OVENS. 





Complete new Catalogue, with over WOO illustrations of 
BREAD and CAKE MACHINERY and OVENS, SHOP and BAKERY 
FITTINGS, &c. 



Complete Catalogue of BISCUIT MACHINERY and 
MECHANICAL OVENS. 



Complete Catalogue of CONFECTIONERY and CHOCOLATE 
MACHINERY. 



See page 353. 



ADVERTISEMENTS. 



XXI. 



JOSEPH BAKER & SONS, 

ENGINEERS AND PATENTEES, 
58, CITY ROAD, LONDON, E.C. 

WORKS :— 

BELL YARD, FEATHERSTONE STREET, & GRAVEN STREET, E.C. 



HIGHEST AWARDS EVER GIVEN FOR 

BAKING MACHINERY AND OVENS, 




BAILEY-BAKER PATENT CONTINUOUS OVEN. 



Pl/iJM£ ajmd Estimates fof{ Fittijnq up Ejmtif^e 
Bread or Biscuit Factories, &c. 

MANUFACTURERS OF 

MACHINERY, OVENS, AND UTENSILS 

OF EVERY DESCRIPTION FOR 

BREAD, BISCUITS, AND CONFECTIONERY. 

Complete New Catalogues with over 1000 
illustrations. 

Seepage 359. 



XX11. 



ADVERTISEMENTS. 



GOLD MEDAL, South Kensington, 1882. \ SILVER MEDAL, Crystal Pa/ace, 1883. 

THOMPSON BROS., 



1NYENT0RS J MAKERS s PATENT GAS-HEATED OVENS 

SUITABLE FOR 

ffionferttoncrs, f)otri ^proprietors, anb others. 




ELEVATION O F THE " Y ORKSH1REMAN. 

Write for particulars and copies of testimonials. 



ADVERTISEMENTS. 



XX111. 




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O \£ 

ex a 



si 






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•S B 

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XXIV. 



ADVERTISEMENTS. 



SWIFT & SON, 

OPTICI^-ITS, 

UNIVERSITY OPTICAL WORKS, 

S\, {Tottenham Court 1Roa&, %on&on, TOU 



SEVEN GOLD MEDALS AWARDED. 




Swift & Son's Microscope, specially designed for the use of the 
Miller, Baker, Brewer, and Botanist, and for general scientific 
research, with two Objectives and Eye-piece, as shown in wood- 
cut, in Cabinet . . . . . . . . . . . . . . £5 5 

Or, with the addition of Mechanical Movement for coarse focussing 6 15 

Extra apparatus if reqxiired : — 
Polariscope . . . . . . . . . . . . . . . . 14 

Additional Eye-piece . . . . . . . . , . . . . . O 10 

-£-in. Objective 3 

Life Box for pond life . . . . . . . . . . . . O 5 

Stage Forceps and Pliers . . . . . . . . . . . . 5 

Illustrated Catalogue for stamp ; also, list of Swift & Son's Photographic 
Paragon Lenses for stamp. 



ADVERTISEMENTS. XXV. 



J. ORME & Co. 

(Late M. Jackson & Co.,) 

APPARATUS & CHEMICALS 



FOR 



Students, Lecturers, & General Laboratory Use. 



By appointment to the Science and Art department, Phar- 
maceutical Society, Royal School of Mines, &c. 



BALANCES, MICROSCOPES, 



AND ALL OTHER 



APPARATUS AND CHEMICALS, 

Required for performance of experiments 
described in this work, supplied. 



Complete Catalogue, with neatly 1,000 Illustrations, post-free, 2s. 6d. 
Chemical Apparatus Catalogue, 660 Illustrations, post-free, yd. 



J. ORME & Co., 

65, BARBICAN, LONDON, E.C. 



XXVI. ADVERTISEMENTS. 



\ 



STANDAED COLOUR SCALE 

FOR 

TESTING THE COLOUR OF FLOUR 

AND EXPRESSING THE SAME NUMERICALLY. 

Invented and Patented by WILLIAM JAGO, F.G.S., F.I.G., 

Analytical and Consulting Chemist. 

Forwarded Post Free, securely packed in Box, together with Description and' 
Directions for Use, to any address in the United Kingdom on receipt of Postal 

Order for 

FIVE SHZILLiaSTG-S- 



PATENT STRENGTH TESTINC APPARATUS, 

As illustrated and described in this Work, see pages 250, 383, 3S7. 

PATENT BURETTE, 

Graduated into Quarts^per Sack, to dough i\ ounces of Flour, with Spring Clip 
and Jet complete, and Glass Stiiring Rod, forwarded Post Fiee, packed in Box r 

on receipt of P.O. for Five Shillings. 

Additional Apparatus. 

Burette Stand 3/- 

Water Reservoir for Burette, India Rubber Cork and Tubing, Clip, &c, 

complete . . . . . . . . . . . . . . . . . . 5/- 

THE VISCOMETER, 

Personally examined and tested — Price, Two Pounds Ten Shilling's 

(Cash with Order). 



The Complete Set of Apparatus, packed in Box, and forwarded carriage 
paid to any town in the United Kingdom on receipt of 

THREE G-TJITsTE^_S. 

YEAST TESTING APPARATUS, 

As illustrated and described in this Work, see page 136. 

This Apparatus consists of Yeast Bottle (a), Indiarubber Corks and Tubing 
(b, c, d, e), and Graduated Jar {/). 

The Apparatus packed in Box, together with 2 lbs. of Yeast Mixture 

forwarded to any address in the United Kingdom, per Parcels Post, on 

receipt of P.O. or Cheque for 

OlSTE O-TJinSTE^^. 



ADDRESS— 

W. JAGO, 138, Springfield Road, Brighton, 



ADVERTISEMENTS. 



XXVI]. 



FIVE GUINEA SET OF ANALYTIC APPARATUS 

Flour Testing. 



Mr. Jago begs to announce that, in compliance with a widely ex- 
pressed wish, he has had arranged the following Set of Apparatus for 
use in Flour Testing. 



THE SET comprises all the apparatus necessary for the 

determination of Moisture, Soluble Extract, Gluten, Strength 

by Doughing Test, and Colour, 



AND CONSISTS OF 



-V 



Chemical Balance on mahogany stand, 
carries 50 grams (if ounces) and turns 
with I milligram (i- grain). 

Complete Set of Weights, from 50 
grams to I milligram, in mahogany 
box, in separate velvet-lined com- 
partments, the smaller weight covered 
with glass ; also brass weight forceps. 

Combined Hot-Water Bath and Hot- 
Water Oven, consisting of Glue Pot, 
with special fittings attached, in- 
cluding continuous Feed Apparatus, 
and 2 ft. Indiarubber Tubing. 

Tripod Stand for ditto. 

6 Small Beakers. 

4 Brass Counterpoises for ditto. 

Steel Spatula. 

Bunsen Burner, and 2 ft. of India- 
rubber Tubing. 

6 Watch Glasses to cover Beakers. 

Glass Measuring Jar, graduated in 
100 divisions. 



3 Large Glass Flasks, with 6 Corks to 
fir. 

2 Glass Funnels, 5 inches diameter. 
Packet of 100 Filter Papers, 10 inches 

diameter. 

3 Large Beakers. 

Graduated Pipette, 25 cubic centi- 
metres. 

Filter Stand, to hold 2 five-inch fun- 
nels. 

3 Doughing Basins. 

Measuring Pipette for Water. 

2 Squares of Silk. 

Glass Stirrer. 

Bottle of Iodine Solution. 

Jago's Patent Burette, graduated in 
quarts per sack, with clip complete. 

Water Reservoir for ditto, consisting of 
Bottle, with tubulure at bottom, 
Indiarubber Cork and Tubing, Clip,. 
&c, complete. 

Burette Stand. 

Standard Colour Scale, Jago's Patent. ■ — V 



Price of the complete Set— FIVE GUINEAS. 
Or including VISCOMETER, Seven Pounds Fifteen Shillings. 

This Set will be packed in box and forwarded by rail, carriage paid, on 
receipt of £$ iew, or with Viscometer on receipt of £%. Every care will be taken 
in packing, but Mr. Jago cannot be responsible for any breakage in transit. 



ADDRESS- 



WILLIAM JAGO, 

138, SPRINGFIELD ROAD, BRIGHTON. 



XXV111. 



ADVERTISEMENTS. 



PFLEIDERER'S DOUGHING MACHINE 

FOR 

FLOUR TSSTIlffG 9 

With REVOLUTION INDICATOR, Complete. 

See page 388. 
Price, THREE P° TT ]tf ^TEN SH ^LU NGS. 

y>i Address, W. J AGO, ijS, Springfield Road, Brighton. 




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ADVERTISEMENTS. 



PERFECT & COMPLETE FERMENTATION 

ENSURED BY THE USE OF THE 

LEVURE-DOREE 



IFIRIEISrOIHI-^Z'IEJk.ST- 




Look to the ''TRADE MARK" which should be on every bag. 

"Use the LEVURE-DOREE, which will produce the best bread and increase 

your trade. " 

Full Directions for use. 



PRICE AND PARTICULARS ON APPLICATION TO THE 

SOLE IMPORTERS, 

J. WATSON & CO., 

61, UNION STREET, 

BOEOUGH, 

LONDON, s.e. 



ADVERTISEMENTS. 



L C.PORTER MILLING CO., 

DEALERS IN AND SHIPPERS OF 

a-IR-A-IUST &c SEEDS. 



Milling Wheat on Orders a Specialty. 
Through MINNESOTA and DAKOTA. 

Export orders for purchases direct from the producer, and through 
shipments, have our special attention. 

We have the best opportunity for selecting and separating for special 
bins or shipments the best Wheat grown, through our thirty Elevators 
in Western Minnesota and Central Dakota. 

Three Inspections made — first at receiving place, second by our 
Travelling Inspector, and again at Winona for Milling and Shipping, 
securing the best of service possible to the purchaser. 

Samples furnished, quotations given, and correspondence solicited. 



PORTER'S PREMIUM FLOUR. 

The " 0000 BOSS " Patent, The " STANDARD " Straight. 
No. 4 " STRONG BAKERS." No. 5, 2a BAKERS low grade. 

These brand grades of flour are not excelled for soundness, as we 
get our supply of Wheat direct from the producer. The W T heat is 
grown from seed specially selected and furnished by us to the farmers. 

The flour is not equalled for purity, strength, and nutritious value 
for consumption. 

We have received Medals, Diplomas, and Special Reports, tak- 
ing the lead in every contest. 

The advantage of securing THE MOST VALUABLE FLOUR 
MADE we now offer to the Trade. 

Samples by Mail Express. Orders for assorted car lots solicited. 
For prompt attention Address — 

L C. PORTER MILLING CO,, 

WINONA, MINNESOTA, U.S.A. 



XXX11. ADVERTISEMENTS. 



QUICK. STRONG. REblABbE. 

The genuine Distillers' Yeast recommended under this head is the produce of 
the choicest Rye and Malt, contains all the properties necessary for a perfect 
fermentation, and has proved to be one of the most effective Yeasts for the manu- 
facture of light sweet bread and small goods. 

AWARDS FOR EXCELLENT QUALITY : 

Prize Medal Baking Exhibition, Berlin, 1884. 

Diploma of Honour, Elmshorn, 1885. 

FRESH DAILY. In 7 and 14 lb, BAGS. 



n. boehme <sc zmhe'stieir, 

14, TRINITY SQUARE, TOWER HILL, LONDON, E.C. 

MILLERS 

Are recommended to have 

THEIR FLOURS TESTED WEEKLY, 

or at other regular intervals, 

FOR STRENGTH, COLOUR, GLUTEN, AND MOISTURE. 

A Comparison of the Results with the Wheat Mixture 
used, will afford 

INFORMATION OF HIGH PERMANENT VALUE. 



IB .A- :k: IE IR s 

before purchasing Flour 

SHOULD HAVE SAMPLES TESTED, 

and select those which are of the best value at the 

price. 

SPECIAL TERMS ARE QUOTED 

FOR SERIES OF PERIODIC TESTS, OR FOR LARGE 
NUMBERS OF SAMPLES. 



ADDRESS— 

WILLIAM JAGO, F.C.S., F.I.C., 

138, SPRINGFIELD ROAD, BRIGHTON. 



ADVERTISEMENTS. XXX111. 



^be Bortb^Westetn fllMUer, 

Published WEEKLY, at Minneapolis Minn., U.S.A. 

THE LARGEST MILLING CENTRE IN THE WORLD. 

Will be sent post paid for one year to any foreign address for 16s. 8d., 
53 numbers, including the sumptuous Holiday Number. 



All Millers and users of American Hour will find the NORTH-WESTERN 
MILLER of constant use and value to them in keeping themselves fully 
informed as to the course and progress of the American milling and grain 
trades. 

" A triumph in trade journalism." — Millers' Gazette, London. 

" The Holiday Number of the North-Western Miller forms an 
unique specimen of trade journalism." — Machinery Market, London. 

" Mr. C. M. Palmer stands unrivalled as the publisher of the finest 
issue of a trade journal in the world." — British and Foreign Con- 
fectioner. 

" We would not care to be without the weekly budget of trade 
news, crisp and fresh from the mill and in a readable form ; enter- 
taining as a novel and instructive as an encyclopaedia."— -John Glass 
6° Co., Flour Manufacturers, Glasgow. 

" It is noted for the excellence and beauty of its make up, and the 
entertaining character of its contents." — New York Tribune. 

" The standard milling paper of this country. The North-Western 
Miller is a journal which thoroughly responds to the trade it repre- 
sents." — New Orleans Times-De?nocrat. 

"The North-Western Miller is so far in advance of its rivals 
that no lash and spur on their part will ever close the gap." — North- 
Western Licmberman, Chicago. 

" The North-Western Miller is a revelation of really what meri- 
torious things can be done in the West." — Ma?iufaciurers r Gazette, 
Boston. 

" It is singular that a trade journal, the North-Western Miller r 
should have produced the most artistically printed production this 
season west of New York." — Argonaut, San Francisco. 



The Holiday Number above referred to is sent free to all regular Subscribers 

in addition to the weekly issue. 
Copies of the last issue, with its beautiful Albertype cover " Don Quixote 
Charging the Windmill," will be sent post paid for is. 6d. 

Subscriptions may be forwarded direct to the Publisher,. 

C. M. PALMER, Minneapolis, Minn., U.S.A.\ 

Or, to the Agents in Great Britain, 
Messrs. FLU GEL & CO., 8, Market Buildings, 26 & 28, Mark Lane] London, E.C 



JXXX1V. 



ADVERTISEMENTS. 



Established 1st March, 1875. 



W. DUNHAM, Proprietor. 



The Largest Milling Paper in the World, 

And the First Established in the United Kingdom. 



TECHNICAL ISSUE. 




A "WEEKLY JOURNAL DEVOTED TO THE INTERESTS OF MILLERS 

hblhhed eocry Monday Evening, lit ilmojor tie Kails, at Iho 0ffct.2\, Hani Lam. London, £& 
IS^ElzSiF® LONDON: MONDAY EVENING. FEBBUAOT 5, 1883. •Tgj^<~Sg: r >& 



Milli. &c, to be Let, or Sold. 

I i.i run 



pon SALE, a FLOUR MILL,.itu»u 



TOBELET.immedifti.lv.uponLEASEm 



fJ^BE LET. vnjh^^MOn,. CORN 



I.I I. IIS .n4 CORN MER- 






■JOJIE SOLD.tho LEASE and GOOD. 



TO BE SOLD bv PUBLIC; AUCTION, 



^•riss 1 ^ 






fTHE VERY VALUABLE FREE. 






PI)K SALE, near M.rbrt To™ 

li»il"»'K!i 1 . c SKi s .'..: 

...'■"..'.'." ' .", ' . 



^i^rur.- 






: }.: : ';h' l i r: fi"i 



Machinery, &c.. Wanted. 



RANTED, a - SMITH " 



U[ ANTED, elpht pair, wcond-hanJ. 




1 



Machinery, &c. for Sale. 






i'i. 



pi .ii ii 



R SALE— Tlin-o Pair* of i U-it 



i 



YEARLY SUBSCRIPTION. Post Free to all parts of the World. 

The TECHNICAL ISSUE, published on the first Monday evening \ ^ n , 

in the Month (with Advertisements and Market Supplement) J ua * 

:Single Copy — Technical Issue (containing Advertisements ... ... 5(1- 

TECHNICAL ISSUE, with Market Supplement, and MAR- 
KET ISSUE of every subsequent Monday evening in the \ 12s. 6cL 
Month, in time for the Mails ... 



TO ADVERTISERS. 

The Technical Issue of "The Miller," published the first Monday of 
every Month, has a large circulation in all parts of the world, and is the only 
journal in the United Kingdom devoted exclusively to the interests of Millers. It 
also circulates largely among Bakers, Confectioners, &c. The Technical Issue 
is the best medium for Manufacturers, Corn Mill and Baking Engineers, Mill 
Furnishers, Corn Merchants and others, who desire to increase their business, by 
bringing under notice any Machinery or Specialites suited to the requirements of 
millers, bakers, and kindred trades. 

No Order for any Advertisement can be received on the condition that a notice 
.is to appear in the body of the paper. {Continued on next page. 



ADVERTISEMENTS. XXXV. 






Scale of Charges for Advertisements in Technical Issue only. 

One Page 

Three-quarters Page ... 
Two-thirds Page 

Half Page 

Quarter Page ... 
One-eighth Page 

Under One-eighth Page, at per inch. 

Across Page 

Two-thirds across Page 

Half across Page 

One-third across Page 

Do. do. half-inch and under ... 

Millers advertising Vacancies or for Situations — Twenty words, including 
address, is. ; and for every additional Ten words, 6d. extra. 

Bound Volumes from IV. to XL of " The Miller" can be had at 7s- 6d. each. 
Vols. I., II., and III. are out of print. 



£5 o 





:>er 


insertion 


4 2 


6 




., 


3 15 







„ 


2 15 







j » 


1 12 







., 


16 







'1 


12 









8 







j > 


6 







5> 


4 







,, 


2 


6 







OFFICE: 24, MARK LANE, LONDON, E.C. 



Extract from "Deacons Newspaper Handbook." 

"The Miller" is a paper of comparatively recent origin, having been com- 
menced in the month of March 1875, but in that short time, owing to the great 
■energy and ability with which it has been conducted, it has fairly outstripped all 
competitors, and justly earned the highest commendation of those best able to 
judge of its merits and its usefulness. 

'* The Miller " is issued weekly and monthly, but the weekly edition seen 
alone would not impress one with its importance as a newspaper, unless seen in 
conjunction with the " technical issue " as it is called, which appears on the 1st of 
.each month, and is a massive and striking budget of trade news, comprising eighty 
pages, dilating fully upon all the various topics of the most important commerce 
which it represents. 

Mr. Alderman Hadley, the first president of the British and Irish National 
Association of Millers, bore high testimony to the value of " The Miller." In 
;his speech before the association on the 12th May, 1881, when referring to " The 
Miller" as a trade organ, he said that " in point of size it was the largest in the 
world, and in point of influence it was second to none." 

And the Hon. George Bain in his inaugural address as President of the American 
Millers' National Association at the Indianapolis Convention, May 28th, 1878, 
said, " I never read a copy of ' The Miller ' of London without learning some- 
thing that is worth five years' subscription to it." 

European Continental opinion has also approved very highly of " The Miller" 
as a trade journal, for the Oesterr-Ungar Mueller Zeitung (the Austrian and Hun- 
garian Millers' Journal), of the 28th Jan., 1883, says, " 'The Miller' is well 
known to be one of the most sterling milling trade journals, not only of England, 
;but of the whole world." 
2 G 



XXXVI. ADVERTISEMENTS. 



Wit Jtmrnraii ^tiUet t 

OFFICIAL ORGAN OF THE 

MILLERS' NATIONAL ASSOCIATION 

OF THE UNI TED STATES. 



A Monthly Trade Journal, 



Subscription Price. — Per Year in Advance : 

British Subscribers, Postage prepaid 6s. sterling. 

French Subscribers, „ „ 7f . 50 cent. 

Austrian Subscribers, „ „ 3 Florins. 

German Subscribers, „ „ 6 Marks. 

A Sample Copy sent FREE by Mail. 



-AJPDPI/y TO 

Messrs. W. H. SMITH & SON, 

186, Strand, London, England, 

Who are authorised also to receive Subscriptions. 



ADVERTISEMENTS. XXXV11. 



SIMON'S 

ROLLER MILL SYSTEM. 



TIBIIES PATENT 

REFORM 

PURIFIER, 



With or without Rotating Travelling 
Filter (Dust Catcher). 

In Cases where Dust Catchers or Stive 
Rooms already exist, the "Reform" is delivered 
without the endless Travelling Filter, at a 
considerably Reduced Price. 



HENRY SIMON, 

20, Mount Street, MANCHESTER. 






XXXV111. ADVERTISEMENTS. 



SIMON'S 

ROLLER MILL SYSTEM, 



TEIIE PATENT 

REFORM 

PURIFIER 



One of the best known Millers of the United Kingdom 
calls this " The greatest Invention since Rolls 
superseded Stones!' 



Existing SIEVE PURIFIERS of any system altered 
into "Reform" by my own Workmen without stopping 
the Mill, under guarantee. 

No payment unless promised superior results are 
realised. 



HENRY SIMON, 

so. Mount Street, MANCHESTER. 



